When looking at the gelcoat does it appear to be pitted? If yes then you need to sand and recoat(Gel or paint). If no you could buff and wax. My favorite and very easy way is to get a big can of commet, a good brush and just scrub it till it comes clean. Then I apply Newglass
http://www.newglass2.com(very similar to vertglass
http://www.vertglas.com). Buy the applicator it makes it easy. Just wipe on 4-5 coats. Takes about 5 min a coat. No buffing and the boat will look like new when you are done. The nice thing about this stuff is that the hull will not stain (when you sail in not so clean water) since it seals the gelcoat.
I usually go this at the beginning of each year since my boat(mystere 6.0) sits on the beach all summer.