Steve,
Are you planning on putting on more than a gallon of paint? I put on 1 gallon per year. A light sand to the old bottom paint, hose down with water, dry, wipe down with thinner, dry. Thin paint appropriately. Then, spray whole bottom starting at bow and go around whole boat including keel and rudder. Immediately, go around the whole boat again. Then, a third shot at the keel, rudder and waterline. Should leave a little bit left in the can for where the jackstands and keel blocking were so they can be touched up by hand (or use a Preval sprayer) when the boat is in the slings. A little wetsanding (entice crew to help with beer) and you are all set. No need to sand between coats.