I am absolutely practicing this stuff slow and concentrating on relaxation. Also I’ve found that this is the stage where consciously thinking about helper motions and synchronization is most important.
I’m working on incorporating shoulder/elbow into my motion to get across the strings. I’m finding that also working in some pronation when an arpeggio ends on two notes on the low string, even if that low string is G, helps keep it even as well. I do that for the diminished arps in Glass Prison.
For string skipping, especially going from low to high like in the Solfeggietto, I’m incorporating forearm rotation and also practicing letting my arm/wrist drop and catching it at the right spot to hit the string, then shifting to that back/shoulder/elbow motion to cross pick E B G smoothly.
I think it’s all about synchronization at this stage and helper motions. I need to get a smoother tracking motion and I need it to be precise and second nature. I don’t need to “find” a motion that goes fast here, I need a bigger but we’ll coordinated motion, and to make sure I make it a habit to keep my wrist relaxed and fluid while engaging that helper motion, because adding any unfamiliar motion makes you tense up while you get used to it until it’s no longer a conscious thing.
I think playing faster than you can accurately play at this stage for long periods of time is absolutely bad practice and will result in bad habits. The fast playing thing only makes sense to me in bursts to familiarize yourself or check your motion.