Hi Paul,
It depends on the plastic and what type of paint you use. You will want to test the paint on the hull first. Nothing is going to stick if you rub against some rocks or anything sharp. I would definitely test a small piece of the plastic with the paint first. Maybe an inside piece that won't be seen or is unimportant.

You are definitely going to want to scuff up the hull first so the paint sticks better. Hit it with some very fine sand paper so it has no gloss left on it. Maybe with some wet sand paper or something. That will help the paint stick 500%.

Hope that helps.
5150