There are several ways to remove paint from a miniature. In fact there are four articles on removing paint on this page explaining the pros and cons of over 20 paint removing products. I won't repeat what's in those articles, I'll just say that my favorite paint remover is brake fluid. Pour some brake fluid into a jar, drop in your figures, wait a few days and all the paint will come off under running water. The best part is brake fluid is cheap and works on both metal and plastic figures.