Here's another vote for Meguiar's Marine/RV products. They even have a Fiberglass Restoration Kit
that includes oxidation remover, polish (to bring up the gloss), and wax (to protect your newly polished surface).
I used the kit on our fiberglass roof several years ago. Once it the heavy oxidation was removed, I now use primarily just the polish and wax to keep the roof clean and glossy.