Ablative bottom paint, no barrier coat ditto. Do a quick research on the difference between the ablative type (aka sloughing) and the hard shell type (I used to call it "modified epoxy, but there are more variations now so always look for "ablative" in the description).
For those who leave their boats in the water year round, the hardshell type is more popular and longer lasting, it works by slowly emitting anti fouling agents...but...exposure to air and sun leaches those agents out of the paint with increased rapidity. An ablative paint works by water moving across the hull surface "sloughing" off microscopic layers of paint that take the nasties along for a death ride. The paint is not affected by the elements the way hard shell paint is, making it the choice of sailors who trailer or haul their boats seasonally.
Applying bottom paint is most likely the easiest DYI project a boatowner can have. Just one pre caution, as mentioned elsewhere, if your bottom is fouled when you haul out, attack it immediately because it's way more difficult once the slime drys out. I leave my boat in the water year round, using a reliable dive service to wipe the bottom down monthly. I can usually go 5 years or more before needing to repaint over the old hard shell paint. I always have the diver clean the bottom a day or two before haul out to make the subsequent wash faster and more effective... sometimes I've even been able to avoid the $150 yard fee for power wash with this strategy. Ablative paints are typically renewed at the beginning of the sailing season, right over the top of whatever was left from the previous one. I've never had a boat situation where I used ablative paint, always the hard shell, or none at all, so other's advice might be more relavant than mine. In any case... good luck, have fun.
