Funny you bring this up, I had thought about doing something along those lines on one of the HPI ponycar bodies (probably he AAR Cuda....) just for the heck of it I even found these pics at the time too. It's being applied to a Radio Flyer style wagon, but is enough to get the just of how to do it on an external surface
Hope it helps you some, and definately post up some pics when you get that LB done!