If your lock has a good and powerful mainspring, your flint is sharp without a little round knob that prevents the sharp part from engaging, and your prime is dry, you should never have to touch your frizzen or flint edge. But, perhaps it's out of fear of a misfire or just a head thingy, I sometimes find myself wiping the frizzen off with my thumb, and checking the edge of the flint for that little roller bearing knob. Often when you get a misfire, it's because of that one little spot on the flint that protrudes past the sharp edge, and not necessarily a dull flint. Just remove the spot that is interfering with contact and you'll get instant ignition.