Let the polyester filler cure until material is firm and tack free, about 10 minutes. Sand it down with 80 grit sandpaper until it’s flush with the surface of the fiberglass.
If you’re cleaning a large fiberglass surface, like the hull of a boat, use a power washer to make the process easier and faster, be very careful, as a power washer can actually cut fiberglass and blow chunks right off surface.
The amount of MEKP you’ll need to use will depend on how much gelcoat you’re using and what brand it is. Make sure you follow the manufacturer’s instructions so the gelcoat isn’t the wrong consistency.
When you’re finished, you shouldn’t be able to see any of the fiberglass underneath the gelcoat.
You can buy a gelcoat spray gun online or at your local paint store.
