I'm sure you will get a variety of opinions, but I can tell you what I actually did. I used some leftover Interlux Brightsides, because, well, it was left over. It has been in an often wet and neglected bilge for eight years now and none of it has flaked off, worn off, etc. I did zero prep other than a thorough cleaning. UV is the biggest destoyer of paint. The bilge is actually a fairly benign place for a painted surface. Again, this is real experience. I would not hesitate to use Bilgecoat, if that was your original question.