Not familiar with the tool, but my hunting buddy used to hollow grind his Snuffers by holding/gluing a piece of sand paper to a piece of PVC pipe and then running the blade back and forth on the pipe, using subsequently finer grits of sand paper. Don't remember the size pipe he used or the amount of concaveness achieved, but it was substantial. Of course, pipe size would likely vary depending on the size of the 3-blade head used. A little experimenting would come up with the right size.
Addendum: OK, I just watched the video. Same principal. For glue-on broadheads, I think a piece of tapered wood arrow shaft would be more convenient to use than the plastic broadhead holder. Very easy to rotate 1/3 at a time toward the finishing strokes of the blades.