Back a few years ago I was casting acrylic and rotted wood for a pen making project on a wood lathe. Part of the process was to place wood into a container of heat cured acrylic which filled in most voids in rotted wood. First you pull a vacuum to about 99.7%, let it soak then reverse to 60-80 psi to drive the liquid acrylic into the cellular structure. Then remove and cure at 190 degrees f.. Then you placed the wood into a mold and fill the mold with another kind of acrylic which was pressure cured at 80 psi.
I used the Harbor freight vacuum pumps but could not pull enough vacuum. Had to buy a used Gast pump off EBay. My chamber was a paint pot. First was a 2 1/2 gallon then upgraded to a Binks five gallon pot. Much better made pot and could go up to 110 psi if needed. Never tried to pull oil out of a stock but no reason it would not work if you could get the stock into your chamber or use a vacuum bag like they use to clamp veneer for glueing.
As you approach true vacuum the boiling point for a liquid is falling. Guess at absolute zero pressure the oil should all come to the surface. If you have it wrapped in an adsorbent material most of the oil should be caught but if you don't there is nothing to prevent the surface oil from being pulled slightly back into the wood.
