There are twovery general classifications of bottom paint:
"hard" and "ablative"
The hard paint is just exactly that. Rubbing up against it is much like rubbing up against your home refrigerator. It works because it contains biocides that leach out of the hard, smooth paint.
Ablative paint "ablates". That is, it is built to fall apart. If you rub up against it, it will leaves a mark just as if you had rubbed against a piece of chalk. It works by slowly falling apart. ie: the creatures adhere to the paint, and the paint "fails" locally, and the creature falls off, carrying the surface layer of paint.
Unless the paint is extremely worn, you can detect ablative by rubbing a cloth against it. It the cloth picks up paint, it is ablative; if not, hard.
The two types are incompatible. And some hard paints cannot be applied over other brands of hard paint. You -can- apply fresh ablative over worn ablative.
There are a few "ultra-slick" bottom paints, designed for racing sailboats. But they have reduced bottom protection while adding "slick" to the hull. Expensive and mostly useless for other uses.
Mostly, I'd suggest this:
Determine what type of pait you have. ( Even better, find out -exactly what you have! ).
If you know exactly what you have, follow mfg recommendations.
If you have ablative, slightly roughen up the paint w/ sandpaper, then add fresh coats of ablative.
If hard, things can get more complex. You may need to remove it then re-paint w/ the paint of your choice.
imho.