What I used to clean the walnut stock on my No4 was BLOicon and 0000 steel wool. Dip the steel wool in the boiled lindseed oil and scrub the grime off. Let it soak in for 30 minutes or so and wipe it down with a cloth to remove the excess. (don't let it dry out before you wipe the excess off) Let it dry out overnight an repeat as necessary. You will be really surprised as to how dirty the cloth is that you use to wipe it down