I do not agree that soaking in solvent is always the best approach. I prefer to use scalding hot running water in the laundry sink. The heat softens the preservative on the surface. Brushing with a stiff brush removes that unwanted surface layer. Wipe with old towels or rags.
Sanding military stocks can remove important markings. I'm not talking about the kisses and bumps, but maker's marks and so-called cartouches. Sand a USGI Garand stock and you've turned a potential piece of trade currency into a piece of generic wood.
If you soak the wood in solvent, you will be removing whatever good oil there is underneath. Remember, the arsenal put these things away knowing some soldier would need it later on. Easily getting it back to service condition was their plan all along.
I have a 1 litre bottle of Boiled Linseed Oil, which I rub on cleaned stocks. It works well and is appropriate for almost all stocks.