If you are using roll/tip ensure the particular paint
is designed for that. I believe Awlgrip
is designed for professional application where Interlux Perfection is designed for either spary (pro) or roll/tip. Check out the other paints
and call the tech support numbers and ask if it is suitable for roll/tip method.
I seriously doubt any two part paint
can be applied oevr a one part or unknown paint
without a primer. Interlux has a 2 part primer that is designed for this purpose as the two part paint will eat at the existing paint. When we did our decks we did a lot of prep work but did not remove all the underlying paint. We used the two part primer and then Interlux Perfection (then Interthane Plus) with very good results.
If you want a good job then nothing is better than having a pro spray the paint. You can do all the prep work but no roll/tip is ever quite as good as a really good spray job by a pro.
My next project may be One part - probably Brightsides - and roll/tip but that is due to cost and ease of application. Will probably be ona non skid area as well so even easier.
For a hull I think I would always prefer two part.