Fas-Stone Epoxy filler . Manf by Fasco. Two part. dries white and sands like fiberglass.
Fasco Epoxies
Check the web site for explanation of their products. They can give you list of distributors. I use it for all my repairs, niks, scratches etc. because I paint over it. Very little porosity.
Hermco gives the best advise. Just another alternative here vs gelcoat
