It's incredible all the bad information one can get here. Watertight is a blue green epoxy product designed for under the waterline use and not for gelcoat repair. Most epoxy products are incompatible with gelcoat and are far too expensive for average repair jobs. Use polyester. You can fill "dings" with white gelcoat and if you use the kind with wax, then it will cure without having to apply a PVA (poly vinyl alcohol) product or wax paper, etc. over it to eliminate the air so it will cure. Evercoat also makes a product called gel coat scratch patch which comes in white and is in a tube and designed to deal with simple gel coat ding repairs.