For some slime protection antifouling ablative is the best way to go. You can get Mission Bay
in white but it will rub off eventually, as that is what it is meant to do. While wearing away so should the growth (or at least be easy to rub off). Put some Tuff Stuff primer in white on the gelcoat then paint for the best adhesion. Application instructions on product page.
For a shiny hard bottom look at the Revolution
paint that can be spray or roll applied. You'll want to use the SM 664 D primer
for the best bond. This doesn't have any antifouling properties but can with stand long periods in the water.