What I have done with great success over the years is to go over the stock (stripped of metal parts) with a heat gun to bring the oils and grime to the surface before wiping off with a rag soaked in acetone (available in hardware stores). It may take several applications to get most of it out. A wash with warm soapy water and a clean water rinse, then put aside for 24 hours to dry before rubbing down with OO steel wool. Follow this up with a few well rubbed in coats of Artist's linseed oilicon over a period of a few days till well dried, then polish with a dry cloth.