so what is this technique called and where are some good lessons how to do it.
You dont need lessons for that technique. Its very easy actually. All you need is the accuracy. A clean player does not even always need to put the hand to mute the strings. Its actually much harder to do that same thing while picking every note which I like to do, when it comes to practicing technique.
its called hand over legato technique, and thats a pretty good lesson for it.
So that's a technique that's called legato.... Joe Satriani is pretty much a god among men as far as that goes. Basically it's not really a separate technique so much as just being really good at your pull-offs and hammer-ons. If you just practice strengthening that skill with each finger (hint check out some Satriani tabs), you'll be able to do this with no problem. The "hand-over" is really just a style thing. Normally when you play, you may not realize it, but your picking hand absorbs some of the errant sound of your other hand on the strings. Putting your picking hand at the top of the neck lets it do the same job of minor muting, and looks badass all at the same time.