Sailboat repair question. How to go about filling in gouges on the hull?

I’m repairing a fiberglass sailboat from 1975. On the bottom of the boat, there were lots of bumps (I’m assuming bubbles in the gelcoat.) My father repaired a sailboat in a similar condition a couple years ago so he suggested that I hit the little bumps with an angle grinder, knock them off, fill in the gouges that made with fiberglass putty (its like a quick drying two part thing) and then sand all the putty down.

I wanted to just sand the bumps down, but since he’d done it before I did what he suggested. Now I’ve got little gouges all over the hole of my boat, with fiberglass putty in them. The putty, although quick drying, is still tacky after 3 days… which has made it nearly impossible to sand, as the tacky putty gets all over the sandpaper.

At this point, I don’t have a clue what to do to make my hull smooth. Any ideas/suggestions would be appreciated! Thanks