I heard 3m makes a good gelcoat restoration (bufing compound) product for severly oxidized surfaces. A company called Collinite makes a great finishing wax, #845. This product is the most durable wax I have ever used.
Yacht Brite Buff Magic followed by a coat of Collonite 885 Fleet Wax. You won't need to touch it again for a year. Mine is going on 18 months now in a salt water environment and the hull still shines and beads water. A little labor intensive but worth the time - if you have it.
However. a fresh water bath with boat soap after every trip.
