I have done a lot of restoration on surplus gun stocks, and just finished one last night on a $39 Mosin-Nagant 91/30. I thought I would share my experiences with those of you who might be interested.
Someone on this sight suggested using oven cleaner to remove grease/oil from a oil soaked stock. I tried this for a second time last night and had fantastic results. I couldn't believe how much grease and dirt came off of the stock. I just wiped off the cleaner/grease/dirt and then wiped with a wet towel to remove any remaining residue.
Last nights particular stock did not have much finish left. Although it was clean after the degreasing, it needed something to restore the original look. I usually use Tru-Oil for hand rubbed finishes, but have found it to be a bit too glossy for military finishes, and I was out last night! So, I tried some Minwax semi-gloss quick drying finish. It worked wonderfully. It took two coats to restore the finish to what the handguard had left, and match closely to my M91's original finish that did not need restoration. The 91/30's stock looks fantastic compared to the way it showed up at my door. I did not try to remove any marks or dings in the stock, to retain it's "battle used" look.
If anyone has an old battle rifle that has a similar problem and wants to clean it up. This seems to work great, and doesn't really change/modify/mess up the original look.