It is incredible that you posted this so recently as I just read that very chapter about an hour ago looking for any insight into how to make a full set of drivers out of drill rod or some similar material.
Unfortunately it was not addressed in the chapter do you have any insight into it?
I was thinking of using the Brownells stone and taking a predetermined length of rod and gripping it in the machinists vise and just grinding.
Then epoxying on a handle. Does this seem feasible?
Also I was searching around and found this neat device. Not sure if it is necessary but it does show there is a need for custom ground drivers.
http://www.kokopelliproducts.com/screw.html
Probably have seen it before and I am unsure of its practicality when a machinist vise can be used just as easily.