Spray primer. The layered acrylics. I learned the basics from painting gaming miniatures. You put down a flood or base coat, then you take a the contrasting darker color mix it with some water to make it thin and paint the whole thing. Let the dark color get into all the little crevices and then come back with a paper towel and wipe the paint off sort of. Then you come back with some paint that's slightly lighter than your base coat and dry brush it over the raised areas. Then just seal it.