This article is intended for the novice painter, customizer, or doll-maker--although someone with more experience may glean a bit of information from it. This isn't intended as a color theory article or a comprehensive guide to painting. It's for using Testor's Acryl paints for custom figure resin painting. For more comprehensive information on painting with acrylics, please see my other article on painting here.
What I've attempted is to share a few things that have struck me as significant in my migration from canvas to plastic (I’m a fine art painter). Specifically, I've compiled a materials list with a few application tips, geared towards priming and painting resin (plastic).
BRUSHES
Even someone with great eye-hand coordination will produce poor results with poor quality brushes. Buy good brushes! What does this mean. It means money! Spend it. Buy Grumbacher or some professional quality brushes. Also, buy real hair ones. Here’s a list of the types of brushes you’ll need (also see painting page for more specific list):
Spotters
Use for irises and light reflections in eye. These have few bristles that are blunt at the end that make a round impression. Buy a tiny size for the reflections and a bit larger for the irises.
Liners
These have few bristles that taper to a point for refined line quality. Again, buy a couple of sizes. They're great for edging and will allow you to paint minute details (like eyebrows and the whites of eyes).
Flats (Shaders)
Flats are larger with many bristles and usually are blunt at the end with a flat overall shape. Use for dry-brushing, filling in broad areas of color and base coats. 1/4 to 1/2 inch widths are good for doing small scale (Mego) heads. Use the larger for varnishing.
PAINTS
Now that you have good brushes, you will need paints. I've tried several different paints and primers.
Here are my impressions...
Acrylic paints are easiest to work with but may not be as durable as oil-based paints. I prefer acrylics due to my allergies, so I'm going to recommend them to you.
Testors makes acrylic model paints they call "enamel" that are very opaque and very self-leveling. That means brush strokes are less apt to show. They are harder and provide more of a plastic-like finish than other acrylics. However, hard means that they can also be brittle and may chip if they are dropped or knocked.... They have a dramatically different look to them than standard artist acrylics and you will know what I mean when you see one in person. They can be found online and at most hobby stores.
When I want a traditional, simple and clean "Mego" look on the heads, I always use Testors. While I don't always obsess over color matching to the body, sometimes it enhances a figure (especially if a lot of the body will be exposed). Here is a paint formula for mixing flesh that exactly matches a type two Mego body:
Flat White 4769
Leather 4674
Tan 4697
Rot Rlm 23
I can't give you the exact proportions, as I mix it by eye. But it is the best skin match I've produced with any acrylic paints. I’m sure if you play around with it, you’ll discover the proper mix levels. Test it by painting a dab on paper. Mix a small batch using eye dropped to experiment with the proportions. Let it dry so you get an accurate reading, as paint darkens when it dries. Here's a sample of a head I painted using this formula:

If you don't care about color matching, Testors now makes a flesh color tint in their Acryl Model Master line. It's significantly lighter than the Mego bodies, however.
Be aware that Testors paints come in both flat and glossy sheens. If you mix them together, be sure to stir the paint really well.
Note: Testors semi-gloss paints have a sheen that is close to finish on the Mego bodies.
Once you have your paint mixed (mix it in a bottle so you can save it), you're ready to lay down some color. Using your larger flat brush, block in the hair and flesh tones. Try to be neat but know you will need to retouch edges repeatedly to get a good clean look. Don't glob the paint on as this will show in your finished work. Paint should glide easily off of your brush. If it gets runny, you added to much thinner. If paint is too thick, it will be globby and brush will have too much resistance to paint smoothly. A lot of the trick to painting is learning the right consistency to paint with.
To avoid brush strokes with any acrylic paints, you want to paint thin (Testor's is surprisingly forgiving). What does this mean? Patience. Be prepared to apply several if not many coats of paint, depending on the color and type of paint you’re using. To thin a paint, you can either use a thinner designed by the paint manufacturer or, in some cases, water. Be aware that if you use either, it will reduce the opacity of the paint (which means less coverage and more paint layers). Also, too much water can degrade the adhesive properties of the paint. Thicker paints tend to have greater opacity but then there is the problem of brush strokes. In many cases, mixing a very small amount of white or gray to your colors will increase the opacity of the color.
After applying a couple coats of your base colors, you can begin detailing the eyes, eyebrows and hairline. Use your liner for the eyebrows and for painting up to edges. Do not glob the painting on as it will show up as a lumpy finish. Use an off white for the eyes as eyes are seldom bright white. When your whites dry, you may add black irises. Use your spotter for this. It's helpful to draw the circles in first, before painting.
If you go outside of the whites, don't worry. You can touch it up and this is part of the process of painting....
When you are satisfied with the irises, you may add white highlights to the eyes. Highlights look best if placed above center on the same side for each eye. Generally light reflects in the upper part of our eyes, so this looks most realistic.
Continue refining your strokes as they dry and be patient. You'll be more happy with your results if you take your time. It's helpful to paint several heads at a time with similar color schemes as you can keep working, without stopping for drying time.
When your head is complete and dry, you may opt to use Testors Dull Cote as a varnish. Because this is solvent based, I recommend waiting at least one day after painting to use it over your Acryl paints. If spraying, use several very light coats, waiting for it to dry inbetween. If you are brushing it on, you will need mineral spirits to clean your brush and you'll need a good quality, flat brush for this. This will be a dedicated varnish brush. Do not use it with acrylics.
Let your head dry for a day or two and then put it on a body.
Happy customizing.