Dunlop Lemon Oil for the fretboard (wipe off the excess when you're done), and Dunlop Formula 65 guitar polish, which is nitro safe. Incidentally, Hercules stands are also nitro safe.
Linseed oil works, but leaves more of a residue than lemon oil (which is basically high grade mineral oil).
The main thing to avoid is solvents, as nitro doesn't chemically harden, it just dries out.