One trick I have used with good success is to dig a trench in the ground about 4" longer than your stock and 4" deep. Line it with foil and fill it with acetone.
Put the stock in the acetone and place a couple rocks on it to sink it.
Let it soak for about 2 hours. You will have to re-fill the acetone a bit to keep up with the evaporation.
The acetone penetrates the wood pretty deeply and floats out most oils.

Let you stock dry in bright sunlight for a few day and you are ready to re-finish.