First you need to find out what type of bottom
paint is on there now and make sure that the ablative
paint you have will adhere to it. If the bottom is in good shape as you stated, you want to give it a good sand with some med. grit paper. This is more to give a good adhesion surface vs. "getting rid" of what is on there. Many boatyards require that you either put a tarp under your boat while you sand or use a power sander with a vacuum attachment. Bottom
paint is 40%+ copper which is posionous to marine life (obviously) and to humans and other animals. As such, invest in a tevek suit to sand and
paint in as well as a 3M (or similar) respirator with replaceable filters. I would also recommend goggles and latex or similar gloves. (No, Im not a paranoid.) NEVER use water to wipe off the hull after sanding; use the solvent recommended by your
paint manufacturer. I wud also strongly recommned a low-tack tape like 3M''s Blue
line to mask off the hull. This comes off very easily and leaves no residue. Generally I use a roller for most of the bottom and CHEAP brushes for places where you cant get at with a roller. MAKE SURE YOU MIX THE
PAINT VERY WELL at the beginning of the process and occasionally while painting as the copper tends to settle at the bottom of the car otherwise.
Paint around the jack stands one weekend and then ask the boatyard to move them so you can
paint the bare spots the next weekend. Dont move them yourself. Good luck. It gets easier every year.