The key to achieving fluidity in playing these arpeggios, is having a relaxed arm and supple, “spongy” wrist. The wrist, I would add is a SPRING, or shock absorber. If you freeze your wrist, you might as well play the piano with a pencil.
I dip my wrist with each inversion, and I roll into the next. The motion is uninterrupted.
A few mental images to help smooth out the arpeggios from octave to octave: ROLLING, CURVING, BREATHING, RELAXED, FOLLOW THROUGH MOTION, CURVY TURNAROUND
About the thumb: It should be relaxed, and played lighter than the other fingers, or else it will intrude, and interrupt the smooth flow throughout the inversions.
The video shows what’s happening in progress, as the arpeggios play out.
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