If the scratch is deeper than the gel coat and you see fiber glass deeper than the gel coat then you should fill the gauge first with resin. Dont use west epoxy
. The gel coat will not adhere to it. The proper resin to use is polyvinyl resin. Then fill with gel coat.
should be able to steer you in the right direction.
If its just a small scratch then using gel coat filler works well.
The trick is to clean thoroughly with acetone then tape the area around the scratch. When you fill it and let it cure take off the tape and wet sand. It sounds difficult but in reality its really easy.
The only difficult part is color matching.
If your doing more than 1 or 2 scratches. Buy a 100 count of gloves. It's much cheaper and you will use them.
Good luck with your project