Originally Posted by Johnny1
I've tried searching but confused between topcoat, flowcoat, gel pat???
Top coat could be flow coat under another name, or could just be paint. Flowcoat is gel coat with wax added that means it cures in air. Gel coat doesn't cure in air. Its designed to cure when air is excluded and to be sticky when in air.
There are two ways to make a fibreglass box. The first is to use a mould - you cover the mould with gel coat mixed with catalyst. The gel goes sticky but on the mould surface goes hard as there is no air on the surface. You then apply chopped strand mat (CSM) to the gel which sticks because its sticky and wet it through with resin (with catalyst). Resin hardens in giving a hard surface. That works well for reproducing multiple of the same object.
Other way, for one offs, is to (as it appears you have) create a box out of say ply wood, cover in CSM with resin and catalyst. If you cover that with gelcoat the surface at the CSM will cure but the top layer will be sticky as its in air. So flow coat is the same substance but contains wax which floats to the surface once applied and creates an invisible air barrier causing the gel to cure.