Hi,
What I do is to count the application of fiberglass as the first coat ...or if the wood is bare and won't get glassed then just rolling on a coat is the first coat of course. I apply 2 more coats of epoxy after that for a total of 3 coats. Three coats is the minimum to guarantee waterproofness. (Is that a word?). I always do sand in between coats, although if putting on an additional coat while the previous is still green (tacky and not sandable yet) then you don't have to. I use 80-grit on all sanding of epoxy, period. I do not work hard to remove a lot of epoxy, but just to let the sanding take off the little tits and points that come from things like whiskers of glass, dust, bugs, etc. If it doesn't snag cloth when it's wiped across it, then it's good enough. "Fill coats" are usually additional coats, applied as necessary and sanded more aggressively to smooth them, that go on after the basic 3 coats. "Fill coats" are generally only necessary on 10-oz or heavier glass, and not even on 10-oz glass that is standard "woven" not "roving". Roving has larger yarn and is harder to fill... not a good type of cloth as the final layer if you want it to be fair. Finally, note that non-permanent things in the boat such as removable helms and furniture (settees and what not that are not epoxied-in permanently) don't necessarily have to be finished with epoxy if they are inside the house, not exposed to weather. More traditional finishes that are cheaper and/or easier can be used on that stuff: varnish, primer and paint, etc. If your accommodations are permanently installed however, I'd go ahead and waterproof them with the usual 3 coats of epoxy, and they don't need fiberglass cloth ...other than decks that is. Think of fiberglass sheathing on a boat as a layer to prevent abrasion (boots and beaches) and/or as protection against sun/wind/rain that would cause checking (small cracks) in plywood or other woods.
Hope that helps.
Brian
