Land...I started with flintlocks back in the 70s, used FFF as both the main charge and for prime...I keep a good stock of it around and just never felt the need to change...My flinters are a .40 and a .54, FFF charges all of them...
I don't worry about fouling, not really a problem unless you use big charges...I plug the vent, pour water down the barrel and much of the fouling goes with it...