This arpeggio tutorial is extremely helpful if you listen to him closely. He talks about the brain and muscle memory, etc. This exactly what I've been talking about for years. Finger speed is NOT obtained by repetition but by use of the mind. At the end of the first video he talks about learning to play arpeggios by holding your fingers down on the notes of the chord. The purpose (as he says) is to lock into your brain WHERE the fingers are on the keys....once they are in the correct position. If they are NOT in the correct position, the brain remembers THAT also. The "holding down the chord" has to be done slowly and deliberately. And, most important, which he didn't say, to linger on the chord for 2-3 seconds and then move on to the next hand position.

I read many years ago, what a concert musician replied to the question: "how many times a day do you have to practice a scale?" The answer was "only once"...if it is done correctly. The brain locks that in and uses that input to repeat.

This sounds complicated and unreal. It's neither of those. It's simply an effective, alternative way to reach your goals in a fraction of the time....when done correctly!