A variety of solutions depending on hull condition
This is a tough one to answer as it depends on your hull condition. Most of the time you can get away with a polisher combo wax. Other times you might want to use a cutter before polishing. Then again if something is really stubborn, 400 wet/dry paper can be used. If presented with a tough challenge, a courser grade sandpaper can be used; remember you don't want to use it tool long in one spot or you'll remove the gelcoat."This Old Boat" is a good source of information; I've bought this book after reading about it here in these forums. It is a great book and will help you out with further repairs you will need to do, now or in the future.