I remember that thread.
Respectfully, I have to ask. What consitutes “faster-than-expected” here? The wrist, forearm and elbow are all capable of tremendous speed already.
I think the effort to devise clever sequences of distinct joint movements in the hope of achieving something faster than a simpler alternating cycle is probably misguided. I would imagine that coordinations associated to the various sequences would be difficult to train due to secondary functions of the antagonist muscles involves. Even if achievable, I’d suspect the coordinations would be highly context specific, meaning a very low return on investment.
It would seem to me a better approach to multiple joint motion is to first understand which motions are compatible based on the primary and secondary functions of the muscles involved. For example, extensor carpi ulnaris has secondary function in pronation, so ulnar extension would be naturally compatible with the pronation phase of a forearm rotation movement. Or, biceps brachii is both a forearm supinator and an elbow flexor, meaning the supination phase of a forearm rotation movement would be naturally compatible with the flexion stage of an elbow movement.
Then, learn to coordinate compatible coordinations as the basic cyclic picking action. These combinations might complement each other, facilitating actions not impossible for either joint in isolation. Alternatively, these combinations might compound with one another, where both movements facilitate similar actions and where the combinations offers greater robustness and reliability.
I’m well aware that there are players who achieve excellent results with thumb/finger movements (and there are plenty of players pursuing those forms), I can do thumb/finger action quite quickly, and I don’t think thumb/finger movement has any uniquely special advantage over other joint movements for picking fast. It’s always nice to have more tools available and it can give a softer articulation in combination with legato (which is nice), but I don’t see any particular reason to pursue it over other forms.
It can also add length to the stroke, providing greater range of motion.