I have used BLO to finish stocks as well as other wood items over the years - tool handles, etc. Everyone has their own method.
First, Boiled Linseed Oil is what you use - not Raw Linseed Oil - two different animals. For Boiled Linseed Oil finishes, I usually mix up 2/3 BLO with 1/3 Turpentine (real turpentine, not synthetic). I keep a plastic bottle of this mixture on my shelf all the time. The Turp will thin the BLO and help it absorb inn to the wood. This can be done on unfinished wood or stained. I've used it on Walnut, Maple and even Curly Ash stocks. On an unfinished, unstained stock, I always "whisker it several times - this is done by dampening a rag with water and rubbing it in. As it dryer, it will "raise" the grain and then I sand with very fine sandpaper (with the grain of course) to remove the "whiskers". I do this two or three times - even on close grained Maple. After doing this, I let it dry completely for several days and then re-sand with very fine grit paper.
I apply a good coat of it on to the stock in sections with a piece of T shirt - apply a decent coat and then rub vigorously. The turpentine will help carry the BLO into the wood - i.e. it will penetrate. I do this to th entire stock and when done properly, the stock should have a "sheen" to it. I let it dry for several days and then repeat. If I notice any raised grain, I use extremely fine abrasive paper between coats. The number of coats required will depend on the species, the particuly piece of wood and what you like in terms of "looks".
On many stocks, I may repeat this five or six times - all depends on the wood. The "final" coat or coats, I use straight BLO, the same T shirt material and a lot of elbow grease. When done, you should have a nice "sheen" to it.
I have used this method with excellent on plain and curly maple stocks that I first stained with "aquas forte" - an acidic stain that is then heated to turn a dark color and bring the grain pattern of Maple out. (I've used this on most of my custom built muzzleloading rifles that I made in past years).
The nice thin that I like about a BLO finish is that it is a great finish fro a "working gun". Anybody who hunts knows that over time your stock will get scratches, etc. that can't be helped. The gun will be carried in all types of weather - warm, damp, rainy, snowy, etc. When the stock starts to show use, the finish can easily be renewed by rubbing in another coat of BLO.
Recently, I dug out an old GEW98 German Mauser that a relative had brought back from WWI in 1918. I reload and I wanted to put this "old girl" back to work after sitting for 95 years. It is a "1905 Danzig" and the stock has lots of "well earned" bumps, scratches, etc. from actual combat use. I didn't want to technically "refinish" the wood so I just carefully washed it with a damp rag and some mild soap and then let it dry for a few days. Usint the 2/3 BLO and 1/3 Turpentine mixture, I applied it with a T shirt rag and spent a lot of elbow grease in rubbing it in. About four coats brought the wood back to live again and gave it a very nice sheen that will withstand what "range wear" it will get. Since I had the barrel and action removed, I also rubbed the mixture into the barrel channel and action mortise - it will act as a protection against any moisture that could find its way in there.
If you are going to refinish stocks, etc. - the best way to learn is to just jimp in and do it. If you want to practice first - try and find some wood scraps out of the same species - i.e. walnut, maple, beech, birch - whatever the stock is made from. The practice on the scrap. Keep in mind that every piece of wood is "different" and will accept finishes. Old wood will accept finishes differently than "new" wood.
In applying finishes such as BLO, lacquers, varnish, etc. - a number of lighter coats built up are better than one "heavy" coat. Allow drying time and don't get impatient by trying to do it in one day. Good luck and have fun!
