Oh God, I can certainly feel for you.
As a complete waste of time, try sanding out the flat tops and hollows using a small piece of #1,000 grit wet/dry emery paper and a dental pick. I've managed to repair small areas (about 1/2" square) of non skid using this method and if you spend enough time and are a bit of an artiste, you can get a near perfect match to the pattern of the non skid.
Next, try acetone. It does NOT attack gel coat regardless of what the old wives say. Try applying applying with a Q-tip first to see if the acetone will dissolve the paint. If you're lucky this MIGHT work. It's going to mess up the edge of the hatch a little but this can be brushed over using some Krylon sprayed into a piece of aluminum foil.
NEXT, try lacquer thinner but try it on a hidden sample of gel coat first as it MAY harm the surface. Nasty Stuff.
Lastly, kick yourself for not removing the hatch first.