I would say just be sure that you use a primer suitable for plastic, will be compatible with the paint you have chosen, and is also suitable for marine environments. I just painted a fiberglass boat with VC 17M, and the manufacturer recommended starting with 5 coats of Interprotect epoxy paint to prevent blistering of the fiberglass. With plastic, I would think blistering would not be an issue. Also, the Interprotect sets up fairly rough, so I had to do some significant sanding in order to get it smooth enough.
I recently painted the bottom of my plastic H170 and used Krylon spray paint. It worked pretty well, but I had to sand in places to smooth out the overspray. I don't keep my 170 in the water, so I did not apply any anti-fouling paint.
Prep for you will include pressure washing then sanding to get off any stubborn residue. You do not want to apply anything until you have it all nice and clean.