[Austin W Hogan]

I have found heating and cooling cycles will drive oil out the end grain. Immersing the wrist in solvent will thin the oil, and help it diffuse out. I have immersed the wrist in a can of solvent and put the stock butt up in the sun. As the butt warms it drives the oil into the solvent. An infra red lamp might let you do this indoors. Change the solvent often to prevent return flow.
I once used a microwave oven to drive the oil out of a hammergun stock with no metal. It works well to get oil out of the first half inch of end grain, but it doesn't produce the temperature gradient necessary to drive out deep oil soaking.
Best, Austin