The hull looks as though it may be from the Percassa class stables in the beginning of its life and by the photographs it looks in pretty good nick. If you want to skin it; you have a couple of options
You could coat it with about 3 – 4 coats of Zepoxy finishing resin which would seal the hull and if you rub it down between coats, it will give you an excellent surface to paint on. Or, if the plywood is a little bit ‘iffy’ in places, you could go for a coating of polyester resin on the skin of the hull followed by a layer of finishing tissue matting/very fine with a couple of coats of pure polyester resin over the top of that and this could be rubbed down. Dont make the mistake though of using the Halfords supplied tissue matting with the epoxy resin – cos the bonding agent in the tissue matt is not activated by the epoxy resin it is only activated by polyester resin.
If you want any further details on the RTT launches = do a search of this forum and you will come up with the build I did and several others.