It might be a good Idea to check out some Illustration classes offered by your local college to learn more design basics, graphics and color thoery... Some schools also offer airbrush illustration courses... I am currently a Creative Director in the Advertising field with about 20 years of experience in Design and Illustration... I do all of my own paint work on my projects and graphic design backgroud comes it handy, plus it gives you the kind of eye for detail that you need to do body work as Bob mentioned above...

Hope this helps...

Dave Brisco