Something I have used to take the oil out of mil-surp stocks is a soap called Purple Power that I bought at an auto parts store. I am not sure, but I bet it is very similar to Simple Green. I put it in a pump spray bottle, disassembled the rifle and put the wood in the shower. I then sprayed it down with purple power and let it sit for about a half hour. Most of the time the stock was bare after 1/2 hour. A couple times I have had to do it twice. It didn't seem to stain the shower at all since it is soap. This stuff will take all the moisture/oil out of your skin. I have used oven cleaner, but it is more of a pain with the fumes and the skin irratation. It must be done outside etc. However the oven cleaner works great on plastic finishes like polyurethane.
I have used both tung oil and BLO. For the mil-surps I always use BLO since it leaves a nice matte finish. Just as an experiment, I took a Marlin Model 25 in .22 Mag and refinished it's stock with tung oil. The stock looked terrible out of the box. I spend a month or more building up two coats a day. It is gorgeous now although I probably did this three years ago and never put the rifle back together.