Shellac is a horrible choice, it won't give even the most rudimentary protection from moisture.

If you want the stock stained, apply stain and adjust the color.  Tru Oil is a superior stock finish that will yield an excellent finish if it's applied correctly.  Don't use a filler unless you want to use one with black on American walnut to bring out the grain.

Cut the first application of Tru Oil so it will soak into the wood.  Build up four to 8 very thin applications so the wood will be well filled.  When you rub out each coat, examine the finish in a glancing light so you can see the defects, in particular cloudy areas, and rub it out before proceeding to the next coat.

It doesn't matter.  Every finish we use except maybe epoxy will darken with age, so chasing color is probably a waste of time in truth, because it's going to change anyway, and in not very many years.

Here's what I've observed about the first one or two stocks stained by most people - they aren't nearly dark enough, although you will think so until the stain has dried for a couple of days.  The best thing I know to do is to compare the color to another gun and don't stop staining too early.

If you want to color Tru Oil, I wouldn't be afraid to add a little burnt umber colored oil paint or dry tempera paint (not real egg tempera!) from an art store, but I would try it out on a piece of scrap wood first.

Tru Oil is a modified linseed oil that polymerizes when it cures; I don't know if a tiny bit of oil paint will affect the cure, but I doubt it if constraint is used.  And you try it out on a piece of scrap wood, first.

Quoted: When I first started messing with guns, I used some Tru Oil.  I regret it.  Horribly ugly material.  Try to use what was orignial to the firearm.  I am a fan of BLO as a base and Tung Oil as the final coat. Poly urethane is also just plain evil.

Linseed oil is also a poor choice for a gun stock finish, if you want one that will water proof the gun.  For starters, it never cures, even with the dryers added in virtually any you buy from a paint store or hardware store.  It takes months for a linseed oiled stock to remotely cure out, particularly if coats were added before the first coat cured.

Finishing off with Tung oil is an improvement, but it's still not nearly as good as a modified oil.

I'm betting you would be surprised at the number of custom rifles that are finished with Tru Oil, and most of the other finishes such as Linspeed aren't really vastly different.

Polyurethane and epoxy are evil, if you value the guns appearance.  If it's a rifle with a wood stock for hard service in wet and cold, then epoxy is probably the only choice that will seal the stock well enough to prevent shifting zeroes, which is everything for a working rifle.  Just don't leave it shinin'.

Tru Oil is also easy to get whatever degree of shine or matte desired; buff it out for shine, or knock it back with steel wool for the English look.

Quoted: I have had superb results with light and lightly figured wood using Dixie Gun Works chromium trioxide as a base stock stain.   It is easily adjusted for relative darkness by a vinegar wash and on light woods imparts a chestnut like stain. Did a very light Birch mid '60s M/70 stock for a friend and then tru oiled it to a high gloss at his request....The darkness of the stain was easily managed and I deliberately left the checkering I re-cut from the imbossed pattern a darker hue....Surprised myself with the job....Worth a try on a Birch Mosin.   You can adjust the Tru-Oil shine to your liking by doing a heavy rubdown with rotten stone.....lightly grease a chunk of felt about two inches square and then powder it with that abrasive..........do it till it suits you.  The nice thing about that sort of a final finish is its sealing capability for the wood....as someone said, natural oils just don't accomplish that and generally look like hell less constant maintance.

The problem with chromium trioxide is the green color after just a few years, usually less than a decade!

Quoted: Yeah, I heard that too.   That 70 I did is now about 8 years into it's new look and still has the same tone as when it was just finished.   I suspect the greening effect is the failure to "kill" the acid reaction.....You HAVE to do the vinegar wash thoroughly. I also did a Pedersoli long rifle stocked with European walnut with super results and I have also noted no greening with it either.....that ones about 10 years into its re do....The real plus was the highlight it brought to the figure. Do as you will, but it worked for me on two occasions.

You're not the only person that has not had the color turn, but it's not because of the wash, there's something else involved with the wood chemistry, I've never heard an explanation, and I'm sure as heck no chemist.

In any case, I'm not willing to take the chance, there's too much work involved.