I've used Helmsman on a couple canoes and kayaks without problems. I didn't sand between coats either. If I was doing a refinish, I'd sand. Their response sounds like the customer service response I got from Interlux regarding custom tinting their white paint. They told me it couldn't be done, but I tried anyway. I brought it to Home Depot and they mixed the color I wanted. No problems with the paint years later.

Kurt