I've am currently dealing with this on my complete refit
. I am sanding
down with 40 grit and then filling with gelcoat
and then sanding
that smooth. I am prepping to spray the whole deck
mixed with Duratec which helps with flowout and gloss. I removed teak
decks and the decks have molded in non-skid.
In the pictures you can see the first section I did on the left and the section on the right I have sanded and spread the gelcoat on. This is also fairing some low spots.
After I spray the gelcoat finish I plan to tape-off the non-skid areas and roll on Awlgrip anti-skid.
You might try using a stainless wire cup brush in a drill motor
on your painted texture. Try some acetone in spots with the brush or paint
remover and wipe up with paper towels and dispose in the trash.