If it is chips and dents you need to repair, you can get gel coat repair paste. Put on like filler and sand flat/polish until shiny again. If it is general abrasion over a larger area but nothing of any depth, then flow coat and sanding/polishing may be the only way. In my experience on a white hull, I've never managed to get a good colour match though as the old gel coat is slightly yellowed (beyond what oxalic acid will fix).
Phil
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