I picked up on this a while back off Rimfire Central (and I saw in Timberwolf's rifle rebuild thread over on Michigunowners that someone had thrown him the link to the thread there) but their (RFC) user Woodstock has come across this incredibly awesome and simple finishing elixir that's pure magic.
When I used to use straight up linseed, tung, or etc. oils, it would take weeks if not months building up coats--on some older rifles I'd refinished, customers would ask for upwards to 3 to 5 dozen coats so as to avoid having a polyurethane finish.
Woodstock's formula/system is simple and relatively cheap--all you need is spritz bottle armorall and a bottle of truoil by birchwood caseys.
The light lacquer suspended in truoil will react with the armorall, a plasticizer, and create a quick drying epoxy like film.
Wet down the wood with armorall, palming off the excess to leave a wet surface, and then rub in a finger tip's worth--as in just dip a finger tip in--and then start rubbing. At first the wet mess will start to get tacky, but the longer you work it, the tackiness dissipates and you get a glass smooth, and nearly as hard, finish. The first few coats will appear dull, but the luster builds with the coats--so long as you don't rush it or use too much truoil in conjunction with reapplications.
I can't tell by your pics if you've got a solid sap line, but it really adds dimension to the grain on dark woods like walnut. For light woods like maple, birch, or spruce, it won't darken the wood, but will make the blond, lighter grains shine like hair.
It should take about 10-15 minutes per coat. Period. I can do upwards to about 3 dozen coats in a day--rub in a little of the wax compound I described in my last post and it's field ready. No fancy poly coats, no excessive sanding or buffing, and zero wait. I experimented a little with keeping some stashed already mixed for touch up work, and so long as it's a 60% armorall to 40% truoil, it's a matter of pouring a little into the dimple on the bottom of an upside down soda can, stir with a finger tip and start applying.
If it doesn't lose its tackiness outright, it might be from not enough armorall or too much ambient humidity. If that be the case, you might need to let it rest for a couple hours. Rushing coats while its still tacky will leave a build up like someone had wiped a couple boogers off on it. If that happens, a light wipe with a 3m scotchbrite pad pulls it through and cleans it up.
Good luck--hope this helps--and thank you for being an awesome brother, god knows I wish mine thought of me.