Wow.... thanks Guys. This was a long time ago.
Anyway, the fiberglass look was achieved by place a small weave clothe, sort of like a wedding veil material on the plastic part then basically brush painting liquid cement over the material, letting it soak through the material, softening the plastic and then pressing the material into the plastic. once the plastic hardens again as the cement dries you'll end up with this texture. It can also be done with those small clothes used to clean eye glasses for a more random texture.
There is a tutorial on the internet somewhere that I made years ago with photos and descriptions at each step. I'll see if I can locate it and post it here.