Some years ago I built what I thought was going a totally slick 
sharpening rig.  Three Glass plates and a leather strop the plates were 
20" long 4" wide and 3/8" thick

I got some diamond grits for it.  they were the wrong grits. Too fine. I 
really didn't know  much about the  sizes of diamond grits.  Still don't.

I got half,  one, and two micron. They don't seem to make a dent in an 
edged tool.

What three grits would you choose ? Assuming you  know more about this 
than I do.

Know a good source?