we use flitz. microfiber cloth and a jar of flitz just makes them disapear. we have a 23 foor boat and i can do the whole thing (hull included) in about an hour.
what also helps, is when you pull your boat out of the water use babes boat bright. it helps get rid of them and keep your boat looking good.
also babes spot solver works great to get any spots off. WEAR gloves. it burns like hell! haha