To remove oil from an oil soaked stock, start by stripping the old finish. Denatured alcohol will strip old shellac, but other solvents or strippers will be needed for varnishes and other common stock finishes. Use of strippers minimizes sanding which might leave wood lower than surrounding metal. I then start by cleaning the stock with a solution of household ammonia. Ammonia will saponify old gun oil and skin oils, i.e., they are turned into a soap which is water soluble. I then dry the wood and use heat to bring the oil deeper in the wood to the surface where it can be absorbed by covering the wood with paper towels, toilet paper, kitty litter, whiting, corn meal, etc. Another wash with ammonia solution or Dawn dish detergent leaves the surface pretty clean. Old toothbrushes are good to get grunge out of the checkering. Rinse well with plain water and dry.
Only after getting all I can by these methods do I then resort to soaking the wood in solvents like acetone or lacquer thinner, if necessary. Long soaks in harsh solvents do a great job of removing oil, but I feel they also begin breaking down the cellulose structure of the wood. The preliminary cleaning by ammonia, heating, etc. also keeps the solvent from getting so contaminated as would occur otherwise. Even long soaks will not get out all traces of oil, which may have had decades to soak very deep into the wood. So you need to then steam out any dents and refinish fairly soon after de-oiling, because any traces of remaining oil will naturally come to the surface where it may show or interfere with the new finish.
