Unless your gel coat is really oxidizes Mequires paste wax and lots of elbow grease will bring it up. It will take at least two applications.
Do a small section at a time for the first coat and get it off before it dries completely or it will be a bear to get off. Gel coat seems to dry out and the first coat really sticks to it. Once you get it nice two applications a year and it will stay very nice.
PS can we get a spell checker on this board ??