I have used fiberglass a bit when scratch building. The RC planes and RC ships folks use it a lot, and you can get really thin fiberglass cloth at hobby shops (you can get the resin there too). I made patterns actual size of parts I needed, painted them to seal the wood. Then waxed the patter, made a plaster female mold from that, laid up fiberglass inside mold. You can lay up a thin fiberglass outside a male pattern, but the surface will be rough and take a lot of sanding and filler. I suggest you look for RC books to find detailed description of the process. Not as many scratch builders in non-operating scale, smaller models mean less likely to use fiberglass.
The non-operating ship people I know use wood a lot for scratch ships. I am particularly partial to so-called bread-and-butter (laminated) wood hulls. BTW, Ships in Scale, at many hobby shops is a good magazine for scratch building ships.