I feel you here…I felt the same way when Troy advised me to just go all out with an elbow motion. It felt too fast for me and I couldn’t fathom it being usable. Check this out (first clip labeled tremolo only):
I still haven’t tamed it (getting closer though!), but it’s something I’m refining and what’s really important is that it’s fast and smooth. The last day or so, prompted from your very thread, I felt compelled to try some rotational USX stuff out. That really is the end game for me. I probably should post a video to make sure I’m not wrong again lol! But the ‘feeling’ I get when I’m gunning that fast elbow tremolo is what I think I can get going in my attempts at this rotational USX thing now. If I never would have gone through procedure of just going with the elbow, I wouldn’t really know what smoothness felt like at the fast speeds. In other words, knowing what fast/smooth feels is worth its weight in gold if you’ve never felt it before. It will transfer.
One thing last thing I’d mention about an elbow mechanic is that if you feel tensed up/fatigued and you’re only at the 150 bpm range, just try lightening up on your pick grip, and BTW experiment with some different pick grips too. This mechanic can have some tension when it’s all out. This doesn’t look tension free to me:
It is still controlled though. And even still, this is much faster than you or I will be playing most likely So we mortals can manage this motion at ‘our’ speeds tension free, no problem.
Sorry for the TLDR quality of…everything I write. Try out elbow if you’ve seen some speed with it! Just some short bursts, tweaking the variables until it feels like you can play an even tremolo with it. I’d target 150 - 170 bmp. Anything less than this runs you the risk of a motion that isn’t efficient.