A lot of it depends on how dull and chalky the boat is. It may need to be wet sanded, if so it should be finished with at least a 1200 to 1500 grit sandpaper. Usually if it is not too bad use a good buffing compound followed up with glaze or polish, such as a 3M product, and then a good wax.
its not that bad, its just the top part of the boat above the rubber bumper.My custom fit cover ,i believe, had something to do with it. It just recently started happening so i threw the cover away, but the fact that my boat does'nt gliscin drives me nuts.