Finishcoat, also known as flowcoat is the term used for gelcoat which has had wax solution added to allow it to be used as a finish like gelcoat where it is not possible to use a fiberglass mould.
All polyester gelcoats suffer from inhibited cure when in contact with the oxygen in the atmosphere. Topcoats contain a low percentage of wax, which is not really soluble in the gelcoat and floats to the surface. This blocks out the air and ensures a full surface cure. Gelcoat is normally applied to a mould surface which is not exposed.
Wax Solution is added to the gelcoat at 2% by weight to prevent surface tackiness. The gelcoat has now become topcoat and should never be used for anything other than topcoating as resin & gelcoat will not adhere to it. Topcoat is not a high finish paint but it does make a very waterproof hard wearing surface for fiberglass. When dry some brush marks may be evident. When fully cured it can be sanded with wet & dry paper followed by polishing with cutting compound.