Well I there was a thread started on SRP about barber hones (by a fellow who claimed have the 1-in-a-1000-Coticule), you may want to have a read-through.
http://www.straightrazorplace.com/forums/hones/38294-barber-hones-characteristics.html
I think the “general consensus” is 4 to 5 strokes for a razor that is just beginning to lose its keen-ness, then strop and shave, however if the shave does not improve, then repeat 4-5 laps until it does. If the razor is “dull” then it is recommended to hone on a courser hone then finish on the barber hone (that would be the purpose of the double grit hone). But do not “over hone” or you will produce a wire edge.
Now for opinion:
I think barber hones must have worked in some way, or they wouldn’t produce and sold so many… I read somewhere that over a million Swatys were manufactured.
However in my use of them I found in most cases you need much more than 4-5 strokes to sharpen a razor (of course, depending on how “dull” the edge). So I do not believe these hones are fast cutters because you cannot efficiently sharpen a dull razor with a barber hone… some folks will say they cut fact because you can over hone easily… I say a razor that will be sharpened by a barber hone will be close to its optimum sharpness anyway, so it won’t take much to over-hone.
Then there are a few controversial questions… When you get one NOS, the surface is shiny and almost glass smooth… yet somehow that surface can cut hardened steel and sharpen an edge.
Today we get these vintage hones and we lap them and the surface is no longer glass smooth but and somehow we claim that new surface produces the same smooth sharp edge?
Then there is the absurd notion that we can "guess" the grit of a barber hone… lololol Back in the day there was never a standard for abrasive particle size, there was simply Course, Medium and Fine powder for tool sharpening hones. Then FF and FFF for finer particles, then there was 1 minute, 10 minute, and 60 minute powder used for polishing (the time it took for that particle to settle out of water because finer particles took longer to settle)… So no one knows the grit size is in any vintage barber hone... I suspect some idiot on the internet made up that number
: .