That's the general idea of the knapping hammer which to be perfectly honest, I have had very little luck with. I use the knapping hammer as my tapper with the nail tool that I made.

A mizzy wheel is a grinding disk that does not produce as much heat as many of the other grinding stones. As you know if you heat a flint and strike it, it will shatter do when shaping I guess the whole idea is to not heat the flint up anymore then you have to.

I was taking my knife edge (as roundball explained to me) and then taking the knapping hammer and striking the knife very light. So light in fact it is hard to see if anything really came off the flint. The real test of course is if the edge is returned.

Also as you know, never knapp a flint on a loaded rifle. Many people knapp right in the jaws of their rifle and if you knapp right, you will produce a spark.

http://www.americanjewelrysupply.com/products/abrasives/mizzy.html