I use leather. When i take the lock out to clean i spray the flint, Cock, pan, and Frizzen with Windex.
the fouling dissolves instantly, then i rinse with alcohol and follow with a splash of ballistol in the needed spots.
I never remove the flint and leather and the leather takes a good set to the cock jaws and flint.
last session I reached 85 shots with the current flint. bugger just keeps going.