I was watching a video on YouTube on waxing/polishing a boat with gelcoat. They mentioned that the machine you use will heat up the wax enough to bond it to the boat's finish. I believe they were talking about a wax, not sealant. While I could see a machine possibly doing that I doubt one could do that with hand rubbing. While I think a machine could do a great job I am not sure I believe one needs to heat the wax to get it to bond with the boat's finish.