First of all learn to gravity-tap using all fingers, per taubman technique. You have to be good at it.
Second, on the way up (only), apply Edna’s notion of “in and out” to each octave’s (extended) appegio. The in and out element of the “kernel” movement is really a dumbed down version of the mechanism required for the seventh etude in the series.
If you are throwing your fifth finger forward always onto the 10th from the root, you have the essence of the motion. (You don’t also throw the first finger, unlike in the seventh study). The in and out will follow automatically. It’s easy to justify stressing the fifth finger since there is a stress mark in the notation!
Third, the thumb direction is very-out on the first kernel and a little-out on the subsequents (of each phrase). Its rhythmic role is different, the first time! Don’t forget to walk hand and arm, and switch (complex phase) by 180 over the last octave (encompassing a 1-extended-octave ascent plus its descent)
Fourth, on those heading-up (and around) extended-octave motions, remember the “steam train” metaphor for the shoulder and the top of the humerus. Its vital for enabling the “free” taubman” forearm.
You need the forearm to be a “free linkage” (and thus you need the shoulder rotator to be specifically eccentric, to deliver the freedom to the link rod). This caboodle makes the whole mechanism respond/react to the bounce-signal from the keybed as the finger is being tapped. The “systems” reaction to that (tiny) signal will be next finger lifting! (It will lift with subconscious in and out or rotation added in to that custom-lift.) This corrects for the positional-eccentricity induced by the last fingers tap – as it hits the designated note (at some custom angle). Strike too had, the signal is lost in the overload.
In short, going up and around uses a self correcting two-eccentric-rotator rod-linked system, with the shoulder rotator i) responding to the (non linear) linear-direction movement of the main steam piston and ii) reacting to the imbalance induced in the wrist double-hinge!
This is just classical steam train mechanical engineering, for delivering (somewhat irregular compression power) over a bumpy track! There needs to be lots of slack (and re-balancing focused “eccentric weighting”).
On the way down, its mostly right hand (descending) easy double rotations, with hand and arm covering the distances between fingers. Obviously there us a snappy single rotation as you play 1-5, resetting the kernel motion.
Here is an eccentric system – self balancing (reno rodeo carnival):