Zero Buster Charge Question

Hi there, i’ve been playing zero for awhile and i’ve gotten down the sougenmu lighting loop up until the point after the 3 rep where i have to do another lvl 3 buster shot.I cant seem to get another buster shot down, I find it kinda hard to hold down another button down while doing the TK Raikousens so what button/buttons do you guys hold down while doing it?

as soon as i activated sogenmu to begin the loops I start holding down H immediately. And Do Loops with L lightning.

so I charge with H. you could use M also, but if you do the new age L.Loops it will mean you will have to do more buster charge switching.