Just to clarify, what specifically are you going for, convexed edge-bevel only (what he has at 4:00 after working 1.5 hrs) or saber-convex grind to edge (what he has at end after... how much paper and hours work?)?
In either case, you'd be better off on a slack-belt-grinder for the major removal, allowing the belt to grind in stropping action (from spine to edge). SR101 is tough stuff, takes a good while (hours) and lots of patience to reprofile.
By hand (how I convexed my RMD), if your backing is stiff enough and you keep the very edge lifted slightly (shallow angle between spine and strop), you can use circular motions the way he does in the video, working on low-grit until the shoulders of the edge-bevel (behind the first few mm) are ground-away. The circular motion is quicker for removing lots of metal (those shoulders), especially given how abrasion-resistant SR101 is.
But once the shoulders are gone, my experience is that edge-first motion, combined with a rounding surface (mousepad) will dull the edge somewhat by cutting into the abrasive particles on the paper (unlike on a flat, hard-surfaced stone).
What I'd recommend (take or leave): Use a marker to paint the very edge, then grind the shoulders away using moderate pressure in a circular motion as he does (using the new bevel-angle) until the marker starts grinding away. Be patient, it takes a while, and clean/switch paper if the shoulder is not ground down far enough and the blade seems to be skittering off the paper without removing metal - a sign of worn or over-loaded strop, you may go through a lot of paper reprofiling SR101. You may also want to skip the mousepad for this part, as those shoulders can be a bear to remove and the mousepad provides too much cushion (that was my experience).
Once the marker is ground down to ~1mm along the edge, switch to the stropping-motion (and your thin mouse-pad backing), leading with the spine, and use only light pressure so as not to round the edge over (use a fresh surface for good clean removal here). Once the marker is completely gone (again, be patient and use light pressure so as not to 'obtuse' the edge), switch to higher&higher grit and polish to a final sharpness.
I hope this helps. There are others here who have done more re-profiling than myself, so you'll get more advice. I found that trying it oneself will often show one what works best for him/her. Good luck!
