Face Painting - Klutz Press
Ah, Klutz press. Purveyors of whimsical, educational and just darn fun books for kids of all ages (adults are allowed if they play nicely ). Ass with most of their books, you'll get a great introductions and learn the basics first. There is also a section of particularly hard to paint items and how to paint them. Either way it's great fun, and you really can't mess up if you use a child (the paints are non-toxic).