Our natural finish necks use Emmet’s Good Stuff which is a urethane gel that is applied by hand. 

Since it works like a topcoat on the wood, it can be treated as such with any good quality guitar polish. It would be recommended to use a damp guitar cloth, free of any dirt particles that would scratch the wood. We always recommended to have a neck and body cloth and be separate and not shared. Also, always spray the polish directly on the rag and not the neck. 

If there is any excess build up of grime on the fingerboard, it can be removed with a small amount of naphtha applied to a polish cloth. This will break down the gunk and evaporate quickly, therefore not damaging the fingerboard.