Just solvent wash the bottom and apply a non sanding primer...Put the bottom
paint on top of that.
What bottom
paint to use depends on where you live. If you are in a place where winter haul outs are required, use whatever everyone else is using...Dont buy the best because it will loose its effectivness over the winter and you will have to
paint again in the spring.
If you live in an area where you can keep your boat in the water year round, I''d suggest Pettit Trinidad which has always served me well...I have typically been able to get 2-3 years out of a double coat of Trinidad and regular service by a bottom cleaner.