If you've got some time to commit, wash your boat and use the 3M gelcoat (fiberglass) restore products with a polisher (like a grinder but with a sheep fluff pad). A typical random orbit car waxer will not do it here. This 3M product has both a wax and a light polishing compound in them. They have a couple different levels for different levels of oxidation but they work wonders! Wal-Mart usually carries the 'light oxidation' stuff in their boating section and I'm pretty sure Catsailor (here) has both of them.

I just finished doing my 6.0NA yesterday and WOW. I once used the heavy oxidation polisher on my red clay and mildew stained 5.2 and my girlfriend came home asking "O.K....where did the new boat come from" and she wasn't kidding. I still follow up with my random orbit waxer and a good application of some carnuba wax.

NOTE: be sure you tie the boat to the trailer well afterwards - it get's very slippery on carpeted cradels with all that wax.