Not sure what will work best for paint on the fiberglass but you may want to consider step plates whatever you use. I like mine and I think they give people the idea oh yeah step on here.
My truck:
http://good-times.webshots.com/photo/2787626040102454676AnTRGn
Another look:
http://good-times.webshots.com/photo/2195313120102454676csuLch