hi paul. i've always used clear poly urethane for finishing necks. it dries fast and is hard enough to stand years of playing without wearing off..
nitro cellulose lacquer can be used too, but it's softer and needs more time to cure.
i'm sure there's many other alternatives too, but i'd definately go for poly if i were you
oh.. and mask the frets i usually spray the clear over the frets if i need to level them later.