The overall takeaway of his technique is that it is an amalgamation of most every technique. This allows for a breathtaking access to every style and sound. Used with an “economy of motion”, this method of playing will open more musical doors than you can imagine.
It all should be a rather gentle and not-forced action. It is hard until you get it right and feel what is correct. When I’m doing it (thumb, thumb, index, middle) my hand is rather relaxed. I have found that it’s very hard to do the technique with your hand tensed up. Start from a gentle motion, it’s a softer technique not meant really for percussive sounds. It usually comes out as four 16th notes, or a triplet if not using the middle finger.
What most people have been rightfully calling “double thumb” (more like double slap) is a bit different than what i call ” wooten double thumb” and requires a slightly different hand angle. It is a more aggressive, percussive technique where you do need to dig in up & down with your thumb. It usually comes out as two 8th notes and doesn’t involve the other fingers.