I have to say that until a few months ago I have never really been ferocious with wood but I put a few totally oil soaked Bren butts (see thread - 'Take two bren butts' on Bren forum) and just put them straight into a trichloretylene vapour bath. On the basis of nothing ventured, nothing gained. They came out after a short length of time totally clean, oil free and as they say in the Armourers shops, as dry as the padre's ......., er..........., testicles! Anyway.
As you'll see from the state of them, it was a ferocious way of doing things but after repairing the splits etc etc and patching, they came up really well. The wood glue took to the 'new' clean and dry wood and afterwards they boned down, sopped the linseed up and came up as good as anything you'd expect of a working gun. In fact I polished one with some linseed and wax polish and suprised myself.
Maybe someone with a really oil impregnated or varnished fore-end ought to try this tac. A totally alien concept to my apprenticed Armourers way of thinking but it worked for me as you can see by the results