Real black in 2f or 3f if you can get it without too much fuss. 777 if you can't. When I shoot 777, I keep a brush on a rod to break the crust every so often. I used Pyrodex at one time, but it is harder to light IME than either of the others.
I have a conversion that allows the use of 209s in a sidelock with BH209, but haven't tried it yet. Pressures with BH shouod be similar to 777, according to the maker. Probably not a good idea for percussion guns with drum & nipple, or so some say. It was cheap, and an interesting idea, plus it never hurts to have options.
I use Ballistol for cleaning BP and 777, but like gnoahhh said, I've never had rust in or on a gun protected with BF.
