Painting a Boat?

Mabye someone could help me out, how difficult is it to repaint the hull of a boat?

I would not recommend it unless your boat is VERY old. It is hard to get paint to stick to gel coat long term, I've seen a lot of blistering and flaking of painted boats. If you think dry gel looks bad wait till you see peeling paint. If you want to update the look of your boat look into wraps, custom decals or tons of wet sanding and buffing.

I used some hull paint on my old boat and it works for about a season, and now I have some areas that need to be retouched. I am thinking about a solid color wrap for under the rub rail.

I will find out what my friend used,but I know u can use aircraft paint.

it is not that difficult to paint the hull of a boat.You just have to use the right paint systems.If the paint is blistering or flaking like mr king said the painter screwed up.
I,ve painted many skiboats even brand new ones(because of sponsor deals)there is no wet sanding involved and no buffing at least for the first months,,you are just damaging the top coat on fresh paints with buffing.look at inter paints (international marine paints)if you want to paint your boat.start with sanding your boat with a 180 grit,,aply 2 pre coats with a foam roller,sand it smooth again with 320 grit then aply a finish coat with a roller and brush sand it back with a 400/500 grit and aply the last finishing coat.it takes some practice to get a nice glossy finish(like it has been sprayed)
and there are some more issues like the right amount of thinner at the right temperature.Anyway it can be done.another option is a new gelcoat layer or a wrap...but diy paintjob would be the cheapest,you might could some help from a professional for the last finishing layer.
see pic for a roller brush finish
good luck

forgot the pic