I restored a different boat that was in the condition you describe but also had colored fiberglass decks which had oxidized. I used Meguiar's Mirror Glaze #44 Color Restorer, followed by #45 polish. It was a lot of work but the results were impressive.
Does Mcguire still make the Diamond cut product for restoring badly oxidized fiberglass hulls? Ten yeas ago i bought a Potter 15 that was pastell light blue until i brought it back to life. I sold the boat for quite a profit after the cleanup. I have been wet sanding the Omega with 2000 grit to get it done faster due to the heat. I will probably buff the hull with some good quality marine wax like Starbrite. The wet sanding also smoothes out most small scratches and discolored spoth from docks etc. I just spent 2 weeks buffing the hull on a Holder 12 that i have put up for sale. Every evening after the sun went behind the trees for an hour. Patience is not a virtue with me, hince the wet sanding. Charley