At a glance, his picking a lot of the time seems to be sort of similar to Ardeshir Farah, with a combination of forearm rotation and either one or two axis wrist movement. This can result in a kind of “pendulum swing” of the pick over the strings which might even be allowing Jimmy to full-time crosspick a lot of the time (would need a closer look to be sure).
There are places where he shifts into a faster gear, where there seems to be a bit more of a Vinnie Moore elbow thing happening, but it’s not a textbook Vinnie Moore thing, and he doesn’t seem to exhibit the kind of brachioradialis tension we associate with the “hyperspeed” elbow picking of guys like Rusty Cooley, or our forum-mate and CTC interview subject John Taylor. I don’t know if that means part of the “elbow” drive at the “speed burst” parts from Jimmy is partly coming from the shoulder (something I’ve experimented a bit with in the past), or if maybe the need for brachioradialis tension is reduced somewhat by squeezing the forearm against the front of the guitar (something that I think we’ve seen from Andy Wood).
But now I’m mostly curious whether he’s doing full-time crosspicking at moderate speeds.