My research is leading me toward 303 Aerospace Protectant. Yes, you use this instead of wax. It has an SPF of 40, which is critical to maintaining gelcoat. If you go to their website,
www.303products.com, they have some interesting information on protecting gelcoat. They also explain two different ways to apply their product to gelcoat. I have used 303 on my vynil and love it. I have not used it in place of wax, but that is what I'm going to try next.