I had a thought that if they were just slightly different in their scratch pattern, one would tend to cancel out the other. So, I am working at a declining number of strokes on each. The coti I have is significantly faster than the Ch12K

Coti Ch12K
10 30
9 27
8 24
7 21
6 18
5 15
4 12
3 9
2 6
1 6
55 168 total

I am getting some pretty sharp smooth edges. I have examined them under 100x. At the end here I have sizable patches where I see no scratches at all. I am thinking that's good. (sorry can't take pics).

There is no reason I started using these number of passes. I figure you have to start somewhere. I used the WAG principle.