I presume you know what C.Chang says about "speed walls" and "parallel sets". The idea is that if we play 2 notes at the same time, with unison, like a chord, we are reaching infinite speed, because the time between these 2 notes is zero. Now, if we lift a little one of the fingers and let them fall into the keyboard, there`s a very fast sucession of these 2 notes: we come from infinite speed to very fast speed, and this is easier than speed up. For scales, one may do the same thing, first with 1º, 2º and 3º fingers (the 1º down, the 2º with a little lifting, the 3º witha little more) and after with the five fingers. Then, we play 1-2-3 (c-d-e), then 1-2-3-4-5 (f-g-a-b-c). The 1º finger "passing over" (not under) from eto f with the same mouvement we do in chromatic scale. For trills, for example with 2º and 3º fingers: 2-3 a lot of times, then 3-2, then 2-3-2 (when I learned trills, I played 100 times each one of these mouvements everyday. And this does works, believe me. All this hands separated, of course. Please try and see.
Best wishes
rui