What a waste of time and effort some of the suggested remedies entail. Once the gelcoat surface has deteriorated to the point it is rough to the touch, you can trowel wax on it and it won't make any difference. I'm surprised no replies thus far suggest some of the snake oil remedies which are nothing more than floor wax marketed under many different miracle "no hard buffing just wipe it on" products.
Thirty-five plus years boating in the tropics repairing and maintaining many boats has taught me the only fix when it's rough is sanding and painting with a good two part epoxy coating system. The gelcoat is very thin to begin with and when it's worn through, you can't bring it back.
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