First question; how fine of a grit of sandpaper do I need to sand it down to?
The answer to this IMO really depends on the gun one is working on . Normally I sand to around 250-300..
After that you need to whisker. This means you dampen the wood so as to raise the grain . Let it dry and sand dine sand again then whisker again . This you need to repeat until the wood grain no longer raises when you wet it .
I then Burnish the stock using a burnishing tool which is simply nothing more then a piece highly polished steel , Bone , Stone or even a harder wood ..
What this does is compress and polish . Also , you know how some makers , show guns with very little end grain showing around their carving or after the gun is finished with oil , there is no rough look around the carvings . A good burnish helps produce that look by compressing the grain you can get into to whisker .
Second question; I see there at gun stock waxes, gun stock sealers, and gun stock finishes, so I'm not exactly sure of which of these I need to use to get a traditional finish on a LMF Lancaster Maple stained semi-fancy maple stock? My assumption is that the wax creates a high-gloss shine, the sealer fills the pores of a more porous wood like walnut, and the finish adds a bit of a protective layer against the elements and gives it a little shine. Am I correct?
There are I would bet thousands of ways to finish a gun stocks. Which one chooses to use can depend on the gun , grade of gun ………. Doing a proper hand rubbed finish on say a presentation grade shotgun , is a lot different then doing a basic oil or wax finish on a long rifle .
Myself with maple I stain with forties. Then lay up a couple wet coats of boiled linseed . that’s followed with a couple coats of Tung , when dry that’s knocked down and the stock is waxed with an acrylic wax.
Then you also have the Tru-oil . Which can produce a very nice finish. Imo it needs to be knocked back so as to not look like plastic , but that’s preference
Sealers produce a base seal for the wood sealing end grain and such . Depending on the maker , they may not seal the grain “walnut “ without many, many coats , that’s a sealer/ filler
These for the most part are put on after the stock is stained .
Then you have your finish which may consist of different oils , wax’s lacquers………. That goes on top of your sealer .
I would not worry to much about a wax or oil finish that you maybe thinking of using . If they turn out to shinny , they can be simply dulled back with steel wool or a rubbing with burlap
The thing to remember , and I have said this many times through your build .
Don’t rush , take your time .
Same goes for this finishing . Let things dry before you move on to the next step . You wont regret it