gel coat will absorb more moisture than fiberglass will. Grind the gel down, squeegy thinkened epoxy over the surface, block sand till its smooth prima nd paint. Check out epoxyworks on line or look at the Guegen Bros website
http://www.epoxyworks.com/
http://www.systemthree.com/sys3news/...he-epoxy-book/
http://www.westsystem.com/ss/