An Amateur's Tips for Airbrushing Base Coats

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This page acts as a dropping-ground for those various difficult-to-find hints and tips which might be useful for those just starting out using an airbrush for base-coating minis, or for those who might be interested in doing so. It is not a static page - it gets amended as new things come to light. This page reflects only my own experience. Nothing on this page is a substitute for one's own experience or the advice of an expert. i have a limited amount of the former but absolutely none of the latter.

i initially picked up an airbrush in June 2018 to assist in base-coating a large number of wargaming minis. Since then i have upgraded my compressor, purchased a second airbrush, along with spare parts, and consider the airbrush to be an important tool in getting any minis painted. i cannot imagine base-coating them by hand anymore, especially if there are more than a dozen or so to prepare.

i am not a painter! In my trials and errors when painting tabletop minis, i often use an airbrush to base-coat them, but i don't use an airbrush for any sort of "detail work" (for the simple reason that i don't do detail work). Everything i say about "airbrushing" is limited to the context of base-coating miniatures (and similar tidbits, like diorama pieces) unless explicitly noted.

This page is not an exhaustive reference. It's a home of tidbits and pieces which "should" be clear in the larger context. It does not attempt to provide a ready-made compendium, but to convey "supplemental" information intended to compliment more widely-available, comprehensive materials.

Airbrushes can be used to effectively base-coat minis with smooth, even coats at a far lower long-term cost per unit than using aerosol sprays.

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Airbrushing FAQ

Let's get the obligatory FAQs out of the way...

What ratio of paint to thinner? It depends on many factors, such as (but not limited to) the brand and make of paint, the brand and make of thinner, the local temperature and humidity, the air pressure being used, one's personal painting style (developed via experience), etc., etc., etc. There is no single honest answer to that question. Trial and error is the only real solution. With practice, one develops a feel for certain combinations of media, airbrush nozzles, pressure levels, etc., but it takes considerable practice. Do not dismay.
How much air pressure to use? See the previous question. There is no honest answer to this other than, "it depends."
What nozzle size to use (0.2mm, 0.3mm, 0.5mm, etc.)? This also depends on various factors, but boils down to the medium being used, the compressor's capabilities, and one's personal painting preferences. A 0.5mm nozzle tends to require higher pressure (40PSI+ in my limited experience), so may not work well with all low-end nail-art compressors. My personal preferences are, for my preferred paint mix, 0.3mm with 30PSI and (more recently) 0.5mm with 40PSI.
You keep saying "IPA". What is that? It's the common nickname for Isopropyl Alcohol, a.k.a. "rubbing alcohol." Whether or not there's a "real" difference, for this purpose, between 95%+ ethanol and 99%+ isopropyl alcohol is unclear. They both seem to work the same to me. Pre-Covid, both could be readily purchased inexpensively in 5- to 10-liter bottles, but one of the casualties of the Covid response was reduced availability, and higher cost, of both IPA and ethanol. A single 5-liter bottle has lasted me, as of this writing, two years with about a liter remaining.
Priming vs base coating? Some people will want to prime, then base coat, but for what i do that's complete overkill. i only use a base coat of plain paint, with no specialized primer.
Sealing/varnishing? i tend to use brush-on acrylic varnishes (both matte and gloss), and have been known to airbrush them onto particularly large batches of minis. My minis tend to be colored with ink, rather than paint, and certain inks "misreact" with my varnishes, so for such cases i use a thin coat of watered-down PVA (white glue) to protect the ink from the following coat(s) of varnish.
Single- vs Double-action airbrush? My experience is solely with double-action brushes, and i can't imagine using a single-action one. Most airbrushes are double-action, and thus the trigger has two functions: press/release it to begin the air flow and pull/push it to adjust the needle's position. If the needle is mounted ideally, pressing the trigger from its front-most position will release air without releasing any paint, but getting a feel for exactly how to mount the needle takes a bit of practice. (Put simply: press the needle into the nozzle until it just barely makes contact, then affix the needle into place with the brush's mechanism for doing so. Don't force the two together, and don't leave a gap between them, either.)
Can aerosol sprays do the same things? Presumably, yes, but i have "personal aversions" to aerosols and don't use them. For those with extremely limited time, no shortage of budget, and no scruples about what they pump into the air en masse, spray cans are certainly a faster way to base-coat minis because they completely lack the detailed cleanup requirements of an airbrush. Whether the results are otherwise equivalent, i have no idea.
Do you recommend any particular products? See the products section for disclaimers and plugs.

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Top N Tips

Here's a list of the tips i consider to be most important (or most well-hidden deep in random online videos) for those just starting out. Some of these were learned from experience and some were hidden gems in various online videos and forums...

Cleaning Tips

Cleaning the airbrush is a top priority and an unavoidable fact of life with an airbrush. Cleaning-related tips include...

Learn to clean the airbrush before using it. How to clean it properly is the very first thing one should learn. After getting your first airbrush, take it apart and put it back together a few times to get used to it. Don't worry - they're made to do that, and it's a requirement for cleaning them. Cleaning is tedious, but it's a core part of airbrushing and cannot be handwaved away. There are many videos online about how to clean an airbrush, and i recommend watching several, preferably produced by different people. Note that only certain parts of an airbrush really need to be cleaned after each use. The parts around the trigger and air intake, as well as those at the rear of the brush, don't often require cleaning.
Keep the tip clean. The tip of the airbrush will dry and clog from time to time, but this can be effectively eliminated via a simple trick: keep a tiny container (e.g. bottlecap) of alcohol or homemade airbrush cleaner around, along with several cotton swabs. Every five or ten minutes or so, stop painting, dip a swab in the cleaner, pull the airbrush's trigger back (without pressing it) to retract the needle, stick the swab gently into the nozzle cap, and twist it around a bit. Push and pull the brush's trigger (without pressing it) a few times to poke the needle into the swab, but do so gently as it's easy to bend those precision needles or even to bend the nozzle ever so slightly. That will remove any build-up of paint around the nozzle tip before it can become a problem. After doing this, press the airbrush's trigger a few times to burst out some air, which will remove the residual cleaner from the tip.
When cleaning, pull the needle through the front. The most intuitive thing to do is pull the needle out the back, but that drags a lot of paint through the needle housing (which otherwise doesn't often require cleaning). Instead, pull it out the front after removing the nozzle.
Clean the brush immediately when finished. Don't let it sit, giving the paint time to dry on the tip and inside the device. A clean airbrush is (generally) a well-behaved airbrush.
Wear a glove on your off-hand! Not because getting airbrush paint on one's hands is a problem, but because when cleaning the brush (immediately after finishing painting), having paint all over one hand is extremely counter-productive. Pre-Covid, baggy food-preparation gloves could be purchased in packs of 100 or more for about a penny each. The Covid response, unfortunately, has made them more difficult to find at such a price. In my experience the hand holding the brush doesn't get dirty enough to warrant a glove, but my off-hand gets completely covered because i often use it to test the current flow of paint before aiming the brush at the mini.

Generic Tips

Learn to clean the airbrush before using it. See the list above.
WEAR A MASK while painting. Failing to do so can lead to caughing up goop of the same color as one's airbrush paint. Seriously.
Do a "pre-flight check." Before starting work, put some water in the airbrush and make sure that it's spraying properly. If, e.g., a clogged or broken nozzle is causing constant back-feeding of air into the brush, it is better to notice that before the brush is full of paint.
All painting mistakes can be corrected! Don't be afraid to experiment, as most mistakes can be corrected in situ without much effort. Worst case, strip the mini and start over. (A freshly-airbrushed mini can normally be easily stripped with soapy water and/or alcohol and a minute or two with a toothbrush.)
Use dedicated airbrush paint. Mixing plain acrylic paints for use with an airbrush is an exercise in frustration. It will work now and again, but using paint made specifically for airbrushing provides much better results and saves lots of time. Paints can only be thinned "so much" before their molecular bonds break down, and it's not always possible to thin plain acrylic paints down as far as they need to be for use with an airbrush. Even made-for-airbrush paints typically (depending on how they're used) need to be thinned, perhaps by as much as 50%, but this process is much more forgiving with airbrush paints than it is for conventional acrylics.
Practice with colored water. Using plain water is a great way to practice getting a feel for an airbrush without requiring a major cleaning effort. Put a drop of acrylic ink or some food dye into water and spray it around. Water does behave differently than paint, as it's far thinner, but this approach can be used to help get a feel for the controls of the brush and compressor.
Never press the trigger with the brush pointed at the mini, but instead point it off to the side, pull the trigger, get the flow how you would like, then drag it across the mini. FWIW, i tend to use my off-hand (the one holding the mini) as the test target for the paint flow.
Thin, even layers. Never try to slam on thick layers just to be done faster - the results will be far from attractive.
When "spidering" occurs, it's almost always caused by one of: the paint is too thin, the air pressure is off (in either direction), or the brush is too close to the mini. Adjust any/all of those parameters to resolve it.
Splotching has similar causes as spidering, but can also be caused (it turns out) by an ever-so-slightly-bent needle or an air leak. Leaks can happen, e.g., along the edge of the nozzle housing (e.g. if the O-ring is broken or the housing is not on tight), as well as at the point where the air hose goes into the brush. The latter is especially likely for so-called "quick-release" valves, which allow disconnecting the brush from the hose with just a click: in my limited experience, and based on product reviews, those always eventually develop a leak, and i recommend against using them.
Find an airbrush parts supplier. Eventually it will be necessary to replace o-rings, nozzles, and other parts. Having a supplier in advance of the need is not a bad idea. In Europe, wiltec.de offers, as of this writing, o-rings and a small range of needles and nozzles, as well as a wide variety of airbrushes and compressors. (Two years after starting with an airbrush, i have yet to need to replace anything more than o-rings, needles, and nozzles.)

Nozzles are tiny and their o-rings even tinier. Thankfully, the o-rings don't wear out all that often. Even so, having spares of both is a must. These o-rings have been my single-most-replaced airbrush part, and nozzles have had to be replaced a couple times. Note that nozzles are sized to fit a specific needle, so be sure to store them in clearly-marked containers to avoid mixing them up.

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Recipes

Many hobby airbrushers like to use homemade materials when they can, rather than more expensive commercial options, and this guy is no exception...

Thinner

Simply 2 parts water (preferably distilled), 1 part IPA, and "a few drops" of flow aid, where "a few drops" is "somewhere around 2-3 drops per 50ml of thinner." This mix has served me well enough that i have not actively looked for another.

Cleaner

Like thinners, there are dozens of homebrew recipes for airbrush cleaners, most following a common theme: a mix of distilled water, IPA, and window cleaner.

Homemade cleaners, in my limited experience, are generally good enough to get the first 80-odd percent of the job done, but a commercial-grade cleaner may be needed to finish up. i finish all airbrush cleaning with a few milliliters of Tamiya brand cleaner. That stuff is "the nuclear option" of airbrush cleaning agents. If Tamiya can't clean it, it can't be cleaned. Be sure to open all of the doors and windows when using it, though, or it might also clean out your lungs (not in a good way).

The "Red Dragon" Recipe (named after the YouTuber who posted it): 50% automobile windshield cleaner, 40% distilled water, 10% IPA.

That said: there are many variations on that. Some use only a tiny touch of automobile windshield cleaner (or, in its place, Windex brand window cleaner, but that's a U.S. thing) and/or anywhere from 1/10th to 1/3rd IPA. My basic testing suggests that increasing the IPA beyond about 1/3rd doesn't appreciably change the results. Curiously, pure 99%+ pure IPA does not make a good paint cleaner on its own. Plain ethanol works great for cleaning up inks and stripping airbrushed-then-inked minis.

However: honestly, i'm still searching for a great homemade cleaner. The Red Dragon cleaner does the basic cleanup job but i always have to follow up with a stronger (commercial) airbrush cleaner to get the last 10-20% done. Ammonia-based solutions work quite well, but are difficult/expensive to get around here and require good ventilation and a mask (that stuff is strong). Many online airbrushers claim that ammonia-based cleaners are corrosive to airbrushes, but that's "supposedly" (per other online airbrushers) a historical hold-over which does not apply to modern airbrushes unless (perhaps) the brushes are kept soaking in the ammonia for long periods.

In April 2021 i got my first bottle of ammonia-based cleaner (approx. 25% ammonia) and mixed it in with my IPA/window-cleaner-based solution (adding around 10% ammonia solution). It definately improves the cleaning strength, but holy cow that stuff smells strong and burns the eyes. Only use ammonia with excellent ventiliation and a mask. i still use a bit of Tiyama after using such a solution, but adding a bit of ammonia to the mix upgrades the cleaning power of the home-grown solution from the 80-ish percentile to the 90-95% percentile in terms of what it cleans.

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Specific Product Recommendations

By and large i tend to prefer homemade solutions over commercial ones, simply on the grounds of cost, but the fact is that certain products are best left to the professionals. i have personal reservations against buying anything at all from two particularly popular/premium/pricey painting supply brands, but am certain that they produce quality products if one's budget allows for it.

As a rule, i don't like to tell people that product X is "better than" product Y unless i know that to be the case for a specific context. Unfortunately, so much of what goes on with painting depends on many factors, and what is "better" for one user, because of variances in those factors, may well not be "better" for another. That said, what follows is my own personal list of products which i like and can recommend for the purposes i use them for. This is not to say that they are the "best," but they're what i know and what i like (or what i "don't dislike").

Airbrush Paint. Createx #5212, thinned right at 50% when using a 0.3mm nozzle, or slightly less when using a 0.5mm nozzle. This stuff has never let me down, and eliminated the many pains i used to have when trying to mix plain cheap acrylic paints for use with the airbrush.
Airbrush cleaner. i use inexpensive homemade stuff to get the majority of cleaning done, then finish off with a few milliliters of Tamiya airbrush cleaner. That stuff is strong, and a 200ml bottle will last me an estimated 5+ years (but i don't airbrush on a regular basis - a handful of times a year).
Airbrushes. My first one is an inexpensive Gocheer which was included in a set with my first compressor. i like it just fine. My second is a no-name which i also like just fine. Each, if purchased individually, cost no more than about 20 bucks. i use only top-feed airbrushes and have a strong preference for built-in paint cups (not removable/replaceable ones, as those are yet another moving part to deal with when cleaning).
Compressor. My Fengda 196A is actually a generic compressor sold by many different companies under different names, but all of them have the model number 196 or 196A (the difference being that the "A" model comes with an optional housing unit which completely covers the compressor). i chose the 196 model over the 186 only because several product reviews suggested that the 186 runs unduly hot. The 196 does, too, it turns out. (The 186 is also single-cylinder whereas the 196 is two-cylinder, but whether or not that makes a difference is above my pay grade.) It's a powerful, flexible compressor which i hope will continue to function error-free for many years, but it's also admittedly overkill for what i do. My only strong recommendations for a compressor are to make sure to get one with an air tank (that keeps the motor from having to run full-time and helps keep the airflow regulated at a constant value) and to make sure it can handle at least 45-50PSI for long periods (at least an hour at a time).
i initially had an extremely cheap compressor which came as part of an entry-level airbrush kit, but its limited air pressure (around 20PSI) was too problematic for me, plus it could only run for about 20 minutes at a time before it had to be turned off to cool down for at least 5 minutes. (Its main target use is nail art, not minis painting. Even so, it did a decent job of getting me started.)

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