I found a lot of good information in this youtube from Suburban Tool Co. It is not Tormek specific, but is still useful for Tormek sharpeners. The mention of web thinning (4:00) makes a good case for four facet grinding.
Ken
https://youtu.be/c9GkkOg1kDk
Wow. I'm always amazed at how those skilled guys can be so precise when sharpening freehand...
Ah, the benefits of years of experience in a skilled trade!
The DBS-22 certainly gives us a leg up.
Ken