Lots of variables involved in solving your problem, Matt. I can describe what I do, as long as you understand that there are lots of ways of skinning this cat. First, before you worry about shadow and highlights, I suggest you undercoat the figure with paint thinned just enough to flow smoothly off of the brush. There is no formula for this for a variety of reasons, but a ratio of about 1 part water to 3 or 4 parts paint should do it. This coat should NOT be watery thin, but it is better to apply more than one coat of thinned paint than to apply a single thick coat which may be opaque, but also may leave brush strokes due to the thickness of the paint. Before going to the figure, fool around with thinning the paint until you get something that works the way you want it to work. Shadowing and highlighting is a subject which often takes many pages to describe, so the best advice on that issue that I can give you is to look at the how-to articles at this site and others, and in the figure magazines on the market. The absolute best way to develop any technique besides working it out yourself is to get with someone who has it down. Shows are wonderful for this reason. You are right about shadow and highlight being applied very thin, but again there are a bunch of ways of going about it. A key element to success here is to wipe the brush loaded with the thinned paint repeatedly upon your rag or paper towel. Most of the color will appear to come off the brush, but believe me, there will be enough left to get a coat of highlight or shadow on. Repeat this process until you are satisfied. By wiping the brush on the rag or towel, you allow yourself to control the application of the paint without it running all over the place. Good luck and keep your brush wet--Steve Scott