The quick and dirty method I use for milsurp stuff that is oil soaked to blackness is to use E Z Off oven cleaner. I usually do this during the summer (here that's June, July, August) since I like to warm the wood up by setting it in the sun. Get a pair of heavy vinyl gloves like you wife would use to clean the oven with EZ Off, and spray the stock, coating it well on one side. Let it set in the sun for half an hour to an hour, you don't want it to dry out completely, then use a hose and rinse the residue off. The lye in the cleaner will pull the oil out of the wood. Really black stocks may take 2 coats. Do one side, then the other, and get the inletting too.
The caveat (you know there had to be one) is don't over do the applications, the lye will eventually start dissolving the lignin which is the glue that holds wood fibres together. Done right it will save you time like you can't believe. After the wood is dry you may want to neutralize it with something like vinegar. Then once dry refinish as usual. If you did it right you can glass bed it now too. I've probably done a couple of hundred stocks with this method, used to use the whiting (which is a somewhat more mild base than lye) but it's much slower. If you don't want to do a refinish the whiting method would be the way to go. If the wood is really oil soaked you can use the torch method, but it'll take a long long long time to get enough oil out to be able to rebed the wood or add finish in the inletting.