Yes, you can apply bottom paint over polyethlene (plastic). We recommend applying an ablative bottom paint. (preferably ablative such as Cukote.

You should sand the boat with a 60 grit sandpaper, then wash it off with S-80 Cleaner and Dewaxer. After it is cleaned, you should apply 1-2 coats of 1277 bottom paint primer. Let it dry overnight and then apply the Sea Hawk antifouling paint of your choice.