When you investigate your paint products, there will be instructions on how to estimate your boat's bottom square footage. On my 27 footer with fixed fin keel, a gallon of modified epoxy (hard shell) will give me two coats with an extra layer on leading edges of keel and rudder. I leave my boat in saltwater full time, year round... hard shell paint is the choice for that because it works without the boat moving... I would not consider ablative in my situation. If you're going to haul out at a boatyard they may have conditions.... such as type of paint allowed, sanding restrictions and they may require you purchase the paint through their on site store.... but many boatyards in Florida are less regulated than they are here in Calif.
You can extend the life and performance of your vessel if you clean the bottom on a regular basis. Shallow water and a long handled soft bristle brush will usually suffice if you don't wait too long between service... 4-6 weeks. Hard shell paint will stand up to clean much better than ablative... which is designed to slough off as the boat moves through the water.