thats a stock i recently refinished
that flintlock is another i did....
first step is to get the stock off the gun and be working with a bare stock.
next, apply your stripper and remove old finish.
(if finishing a new unfinish stock start here)
sand with the grain to remove old finish that didnt come off, dents, dings, scratches etc...personally when refinishing i dont sand a ton...i'll lightly sand the whole stock but i dont like sanding a whole lot because you will tell when you put it back together..also dont go super fine on the sand paper...i can never remember what grit i use....but dont go super fine.
get all the dust off the stock somehow...
i like to hang them to finish them...i usually put a screw back in that would usually hold the butt plate on and tie string to that screw and hang the stock from something. that way i can do both sides at 1 time and not worry about it at all...
now you can refinish with your choice of finishes.
the first gun stock in the pics i did with satin Spar Urethene. 3 coats of it using fine steel wool between the coats when it was good and dry. no stain or anything before the spar urethene was sprayed on.
the flintlock stock i used a high gloss poly urethane...same thing 3 coats...steel wool between them...
i really like the spar urethene...it seems like a very tough finish as well...you could stain the wood prior to the urethane to get the color you desire...but many factory stocks have the same color wood so you might not have much options...both those stocks had about the same color black walnut stocks...