I've done several stocks now using tru oil but I'm far from being an expert. I seem to learn a little more everytime I do another.
This is the meathod that has worked best for me. After stripping the wood and staining if you prefer I hit it with sandpaper to knock the fibers down. Once lightly with 600 then 1200 wet dry. If the stain is not even I try to keep reapplying, concentrating on the lightest areas then knocking it down until it all matches.
When I start with the tru oil I cut it with mineral spirits, first three coats is 25% part tru oil, 75% mineral spirits. Second three coats is 50:50, and then full on 100% tru oil for the final three or more.
This does a few things to your advantage. First the mix is a lot thinner so it really gets deep into the grain. Second, it is a lot easier to work with. It spreads much easier without build up (runs), it does not get as tacky so no finger prints, brush marks, etc. And third, each coat dries faster, so you can start the next sooner.
I have found for me the best way to apply is with cheap foam paint brushes. It holds the liquid well, and helps spread it out. If one part of the stock has a little too much build up I lay the brush down a little to pick some up and apply it to another area. It also does not leave any fibers, or brush marks. After each coat I squeeze out an excess oil. You can wash them out with pure mineral spirits but I found a bag of ten for $1 at harbor freight so I just bought a few bags and use a new one each time.
After each coat is completely dry I wet sand the stock with a fine wet sand paper using the same tru oil mix that I used on the previous coat. Not only does this knock down any imperfections it also helps fill the grain with the sludge. I then wipe down the excess with a micro fiber towel.
On my final coats when I use 100% tru oil I use a extra fine wet sand.
The stock will obviously look like it has a deep layer of glass on it by this time. If this is the finish you want, I wax the stock at this time.
I havent really found a way yet to get that perfect satin look just yet. It still a work in progress. I've used BC's stock sheen and it works pretty good but I would like to make it just a little more dull so I'm still working on it.