Some interesting suggestions. I think keeping the powder dry is more about how you clean and prep the gun prior to loading, then anything else. Since the wolves have arrived, deer are getting pretty hard to hunt where I am, so I've been having some seasons where I don't fire my rifle...all season. When I empty it after season, it pops off just fine. Easily over a month or so of being loaded. And having hunted on wet days.
If it actually rains...I just stay in the camper and read a book.
If you clean the rifle well, then dry patch it, then clean it again with alcohol patches, and get some down in the breech with the worm, leave it alone for a day, then load, you can leave it loaded for months. In the field I don't stick anything in the touch hole. I think that just moves the main charge away from the hole. I like my main charge packed right up against the touch hole. At night, or at home between hunts, I roll up some paper towel or kleenex and pack that against the touch hole, and lower the cock on it, the flint holds it tight.
Some guys over-oil their locks, or even oil their locks with penetrating oil or WD-40. This will creep up between the pan and barrel, kill the prime and even get into the main charge, and these gents will be convinced that the prime "absorbed moisture from the air". Nope. It absorbed all that oil ya slopped on the inside of the lock.
If the rifle is cleaned and prepped properly with denatured alcohol, at night or between hunts, before you can hunt again some paper towel, rolled or bunched up, and put between the flint and pan, and pushed up against the touch hole will keep any moisture out of the main charge.
It's
amazing how if you don't over oil the lock, the gun will stop absorbing moisture from the air. Go figure.
Actually hunting in the rain, yeah a cows knee will work, but unless water flows directly into your pan, it still won't "absorb moisture from the air" no matter how humid it is. Having the touch hole plugged
while hunting makes no sense to me, but I may be misunderstanding that that was considered. ??