I've never liked TruOil, this goes back to the 60's and my bad experiences with it. Just never got good results, couldn't get the stuff to dry,,except the remaining finish still in the jar. That always dried up pretty well.

Tung Oil I like, but when I use it I like the wipe-on Tung Oil Varnish sold in the Home Depot type stores. Many say there's no Tung Oil in these types of finishes,,That is a long standing often repeated phrase that came from an article printed in a high brow wood finishing/cabinetmakers magazine many years ago that had an axe to grind w/Homer Formby.

Those wiping varnishes are in truth slim on content when it comes to the key ingredient,,in this case Tung Oil. Maybe 15% or even less. The vast content is plain mineral spirits,,75% usually.

But that is how they work in a 'wipe-on' manner.
If you want true thinned consistancy to work with,,you have it right out of the can or bottle.
They make a beautiful 'in the wood' finish. Once that is done,,it can further be built up above the surface if that is what you want.

Sometimes I use plain shellac,,usually orange shellac. I mix it myself with dry shellac flakes and alcohol.
It lasts longer than the store bought stuff and you can mix as little as you may need for a job. Small amts can be stained for use as a toned finish.
Lots of this is in use in restoration work. Shellac finishes are not the best for modern heavy use utility guns but many oldr guns were finished with shellac.

I like to use stain on just about every stock I work on, make, or make over.
Sometimes an oil stain, or more than one color. Sometimes an alcohol based stain or other solvent stain.
Sometimes I use both on the same stock,,allowing drying times betw the two of course.

I fill the grain by sanding in the first coats of the finish. I start with the grit paper of the last grit I used to sand the plain wood.
Then go finer in grit paper with each 'wet sanding' to fill the grain.
AmerWalnut takes more sandings to fill than Euro Walnut as a rule but usually after 4 sandings and let it dry betw coats,,the pores are filled.
The final wet sand and wipe off leaving an absolutely smooth surface will usually be with 800 or sometimes 1000 grit paper.
If the job is a restoration, the pores may be left somewhat unfilled to math the age and look of the orig finish.
It all depends on what you are working on.

You can stop right there and simply put a couple ultra thin coats of Linseed oil on the wood. Really thin,,rubbed out to what feels to be nothing at all on the wood, but it will bring that glow to the surface that really looks nice and not garish.
Let each coat dry at least a few days..linseed is a notorious slow drying oil. Going back over it before it is completely dry(oxidized) is the main reason most Linseed finishes fail to look like they are supposed to.
I put my thumb over the open mouth of the Linseed Oil bottle, turn the bottle over and then back upright.
The amt of oil that is wet and clinging to my thumb that blocked the opening of the bottle is all that is necessary to completely cover an entire one piece rifle stock,,
Dot it around on the stock & hand rub and draw it out as thin as possible.
That is one coat ..let it dry for a few days before adding anymore....

When you feel it's complete, leave it as-is. Or a light rub down with either pumice or rottenstone on a soft pad to dull the gloss to your liking completes the job.