Boy! You really like to jump right in there don't you.. Matching 2 relaticely unrelated pieces of walnut can be really interesting.. I'd clean the butt stock first with a torch and scrapers. Then with acetone or carberator cleaners. This should remove the bulk of the finish and at least some of the oils. Don't soak the butt stock in the acetone too long as it can damage the wood. Also put nothing in the acetone but the wood. If you wish to remove from the butt a paste of acetone and mineral spirits mixed with kitty litter and applied to the wood and allowed to dry. The matching will have to be done with various colors of spirit stains. I have also used leather dies to good effect. I use the Pilkington Spirit stains as they are translucent and blend quite well. It will be necessary to stain both stocks some to get the match. If too much spirit stain is applied a bit of mineral spirits on a rag to wet the wood and blot some of the collor up with a paper towel will lighten some.. I use TruOil and a filler of Behlens Oil Finish applied on hot wood.
