Flip, I assume you used epoxy resin since the figerglass resin eats the foam. I've had good luck thinning the epoxy 1:1 with alcohol for the first couple coats, then adding baby powder to the mixture for the final coats. The powder sure makes sanding easier and it smells like a baby when sanding LOL. I've also tried water based polyurethane, but it is not as hard as epoxy...........Seaplane