Opinions on stock finishing are as varied as on patch lube, or the best pizza toppings.
Don told me he uses Linseed oil and had time to do just a few coats. This is freshly crafted wood. He sent me a bottle of what he uses, and instructions. Knowing how he works, I wouldn't be surprised if he made it himself. I'm very familiar with wood finishing, and know all about Linseed vs Tung and so forth. If I'm not mistaken, it's what was used for generations on these rifles, originally. I'll follow the old:
1 coat a week for a month
1 coat a month for a year.
1 coat a year for the rest of your life.
Not to worry! I know what I'm doing, I've finished a lot of gun stocks. It's very dry here in AZ, even notoriously slow to dry finishes dry in record time, here. I will not put any finish on the gun that has artificial polymers, or plastic urethane. Minwax, Linspeed, TrueOil, and all the others often recommended have that. While most bemoan how long Boiled Linseed Oil takes, and how many coats, I actually enjoy the long process. If it was good enough in the 1700s-1800s, it's good enough for me.
It's kind of ironic to shoot archaic flintlocks with black powder (no Pyrodex here), made with hand forged iron parts, but not to use traditional finishes.