Ok I'll answer this again, but I'm putting up a new post on the Encyclopedia of Gameplay so I don't have to waste time retyping it.
This is just simply Faultless Defense canceling Faust's jumping 2k. To perform it you simply hold the joystick down and back, press and hold kick and then, as quickly as possible, press Slash. You will now be Faustless defending, and using the momentum of j.2K. This is the simplest way to do it. For more elaboration on the subject please read this thread and the Slash General Discussion thread.