A good flint peels white hot steel from the frizzen. The flash comes off the surface of the powder into the touch hole so you don't want to burn powder down to the hole. Position of the hole is important as to how you prime the pan. If too low the powder can stack against it if you move the gun and I don't think anyone will remember to twist the gun when hunting. Best is higher so even a full pan does not block the hole. 4F is for the pan as 3F will not ignite as fast. Course grains can damp out sparks.