I have that Lee Rocker Video. It's not bad.
I would recommend it for someone new to rockabilly slap urb. He explains things very clearly.
Be advised, he advises a few thing in there that a lot of people would disagree with.
For example, he suggests metal strings and specifically advises no gut strings. That's just his preference.
Also, he demonstrates left hand technique that most people cant really reach- i.e. spreading your fingers to cover a half step for every finger, even down near the nut.
So, I guess I'm saying the video is good for right hand slap technique.
There's also this website
http://scotthinds.tripod.com/