Gelcoat isn't paint...so don't think in terms of paint when using it...it should not be done "In coats" ...when it is sprayed it is best to put it all on at once. The mill thickness is much greater than paint, and you want a chemical bond thru out the gelcoat...you will loose that if it is allowed to thoroughly dry, with sanding between coats. What you will end up with then, is more of a mechanical bond, rather than a chemical bond.

Regards,
Bob