There are some GS planes that are covered with film and then graphics are airbrushed on top of them. Check out this link for a really nice example
http://www.aircraft-intl.com/catalog...h/redcheck.jpg

I haven't actually tried to do this but from what I understand the film is lightly sanded to rough the surface and then airbrushed. They usually add an agent to the paint to help it stay flexible and give it more chip resistance.