If you want the natural look, don't scrape & sand the Cetol off your toerails. Buy a hot air gun ($25-$30) and easily scrape the old finish off in ribbons. Then, lightly finish sand with 150 grit - 80 grit if recoating.
The best way I've found for removing dried Cetol from fiberglass, is by either carefully scraping, if only small drips, or with larger areas a very light coating of liquid paint stripper may be necessary - immediately followed by burnishing with a cloth or ScotchBrite pad. Don't allow the stripper to stay on for longer than a few seconds.
Either way, apply rubbing compound and wax to finish the gelcoat. Non-skid Cetol stains will present more of a challenge.
True Blue . . .
sold the Nauticat