Tried the whetstone/grinding stone route with my flints a while back....didn't work too well for me, but it did work better than knapping for some amber flints that I have.
I had a fellow who owns the muzzleloading shop where I buy my black powder and traditional supplies from show me how to do it. He uses a brass clapper from an old bell, and it worked GREAT!!! I'm keeping my eye out for a similar style device at the local garage sales......so far, not much luck.
I'm still only getting about a half dozen shots with my musket before getting misfires.....seeing as how I can get this thing to spark constantly w/o powder in the pan, yet the minute I start shooting it it has poor sparking ability is leading me to believe that there is some type of fouling building up on the frizzen; more experimentation is needed, but I haven't had the time to do it yet.