Advance and throttle notches

[wrndln]

The problem I see is that the flat spots between the grooves made by years of wear would be tough to "sharpen up" with a chisel. Maybe I don't understand how a chisel is used. It seems to me a chisel can only clean out the grooves. If someone can enlighten me as to how a chisel is used to remove the flat spots that are ground down over the year, I would appreciate it. I will be restoring a 28/29 steering column soon, so how best to restore the grooves would be helpful.
Rusty Nelson