[BroadHopper]

Let's face it. When the gelcoat is gone it's gone. All the boat magazines says there is now way to permanently repair faded gelcoat other than to paint over or replace it.
As for temporary restoration, 3M gelcoat cleaner and wax gets my vote. There is a heavy duty one for extreme oxidation as well as a medium. Unfortunately the wax only last about a month. I apply the Bright Star with teflon over the initial treatment. That will make it last the season. The teflon makes it a snap to keep clean.
A trick I learn is to dilute the 3M product in a bucket of water and 'paint' the effected area with a paint brush with it. Then use the buffer. This is a lot easier.