RE: *Fiberglass (Gel-coated) fuse*
Gel coat is a smooth shiny surfacing material on the glass. Not sure what it's actually made of. Gel coat is often colored and is usually the finished surface on boats. For full size boats and race car parts the gel coat is sprayed into the mold first and then the fiberglass goes in and it all cures together. I'd guess model parts are made about the same way.