Regarding shaving armhair at the DMT 1200 grit level:
if you get a great edge in the end, I wouldn't bother. I personally never got great results, if I wasn't already at the "shave hairs"-level at that stage, but if your mileage varies, I wouldn't worry too much. This isn't about shaving arms hair. In the end, It's about shaving your beard.
But, in case you should decide to go back to the DMT after all (which wouldn't surprise me:D), it really does matter for my results how much pressure I apply. I don't apply much pressure in general, but once I get a good TNT result, I really start doing almost zero pressure strokes.
It helps me to add some swiftness to my stroke, although an experienced honer like Randydance often advices against it. But I really can notice how the keenness increases every couple of strokes with that method. I keep a little box with a strand of clean hair, next to me for doing the HHT.
I don't stop till the HHT passes along the entire edge. It's a bit of a dirty version of the HHT, as I need to drag the hair accross the edge a bit, before it catches and pops. It takes me about 50 of those "swift" strokes back and forth, to get from the TNT to the crude HHT.
The Blue:
I only use the blue with a not too dense slurry. With water it's great to practice the stroke, and if you really do a lot of strokes it will eventually remove the DMT's scratch marks, but if you seek further refinement of the edge, you really need a slurry.
From where I start on the Blue, after 50 to 100 laps with slurry, the edge maxes out at a given level of keenness. That's when it's time to go to a yellow coticule, used with water only.
Different razors, different results?
Well yes, but in my experience, all razors so far easily reached shavereadiness with the aforementioned method. Differences emerge in what lies beyond that level. Some razors can be pushed further up the sharpness envelope and still keep good edge retention. The further you step into the realm of ultimate keenness, the more unpredictable it becomes how a razor responds to a certain treatment (such as stropping on CrO). But all my razors shave arm hair off the DMT, and they all shave well off the coticule.
Bart.