Here’s my method, and some pics of what I have done. I use Behr 600 Tung Oil Finish (TOF), but it has been discontinued as a Behr product, but it is now sold as True Tone 400 Tung Oil Finish. I’ve heard it is sold at Ace, but you might want to call Behr and see if they have any 600 left in stock. I highly recommend this stuff over the Formby’s products.
First, to clean a soiled stock, I coat the stock with Fume Free Easy Off, let it sit for a few minutes, scrub with a stiff brush (making sure to not catch any splinters that may rip from the grain), then rinse with extremely hot water in the kitchen sink. Turn your water heater up to scalding level to get the water hot enough for this, then turn it back down afterwards. Some people will say that the Easy Off method destroys the wood, but the Fume Free version is a different type of chemical and only serves to cut the grease and grime on the stock. Using extremely hot water will remove all of this, and it won’t penetrate into the wood, but it will raise some of the dents and dings in the stock. After this, place the stock to dry for a couple of days.
Once it is dry, start sanding, working to progressively finer grits. If it is a historic stock with cartouches, protect these from sanding. Some stocks only need a light sanding with 150 grit to knock the hairs down; others that have more dents need more sanding starting off with 60 grit. Remember that dents and dings will be much more apparent once you start oiling the stock. One trick I use is to use Walmart Carb Cleaner to spray the sanding dust off the stock, and doing so shows what dings will be apparent once it is oil. It also doesn’t raise the grain.
Once you are done with your final sanding, use 0000 Steel Wool and apply the TOF to the entire stock. The first coat will soak in pretty quickly, so makes sure the surface is coated pretty well. Let it sit for 10-15 minutes, then completely remove the excess with an old sock. Let it dry for a day or so. Repeat this for at least four coats. The coats will build on each other and eventually give a semi-gloss finish.