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 with
gelcoat 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.