I prefer not to add any type of coating other than wax to the beams when seating them since any other type of coating will add space between the beam and the hull you are trying to eliminate. I've seated a ton of boat beams/hulls with only waxing the beam (partall wax) and using a thickened epoxy resin mixture (will use gelcoat in the future as it doesn't yellow and will match the hull). With this process, it only takes a gentle tap with a rubber mallet to get the beam to release once cured...PVA, wax paper, etc. is not needed. The aluminum doesn't like to stick to resins as it is - the wax gives it just a little extra incentive to not stick.