The easiest way for me to utilize that move is actually from a wrist mount.
If I throw a wrist mount, and then dismount it by spreading the bucket with my freehand, and then swinging the yoyo out through the top gap/hole of the bucket toward my freehand, by the time it starts swinging around into a man on the flying trapeze with his brother and sister (a backwards 2.5 mount) I can slide the strings off of my free hand and whip with my throwhand into that mount.
this is probably confusing as heck... but maybe it'll help.
EDIT:
It looks like he did it by doing the following:
A. 1.5 mount (like the beginning of Buddha's revenge)
http://kwos.ca/yoyo-tricks-advanced/advanced-yoyo-tricks-kwos-buddha.htmB. Then he did an underpass to get into a double or nothing with the loop around both fingers.
C. Then he swung the yoyo to his left (or right if you're lefthanded), let the yoyo swing under and then up toward his throw hand, where he pinched the string with his throwhand thumb
D. Then whipped the string into the mount.