I would suggest before painting do a sanding with 200 grit (higher if the boat will be used for racing) to roughen the hull up for the paint. Remember the higher the number on the grit the smoother the smoother the finish will be. I recently completed a similar project on a Hobie 16. I sanded down to 200 and brushed the paint on and it came out fine. You want to apply a few thin coats instead of one or two thick coats. My experience has been priming is a step thats only needed if the surface is in poor condition. The result is well worth the effort. If you have any further questions I will be glad to answer them.