Juicebox Able made it really clear to me on one of his streams the other day.
The input for

can be done very very fast. From what he showed me, and what I've been doing the past couple says, I'm starting the charge before

is out. As long as the timing on the end is right, you'll get it everytime. It's very simple in all reality once you see what is going on.
The jump in has helped my timing with it quite a bit as well, I don't know why though. This really opens up so much damage with minimal meter for Takuma.