Wako Vatista Compilation - UNIST 

powerpsi / he's just buffering the gem hold while doing other moves so that during the plus frames of the gem detonation, he can set another one. Doing that is a matter of muscle memory, yes. But keep in mind that without detonating a gem, doing a normal into a gem set is minus in most instances (punishable, in fact). In the confusion of the moment, along with the fear of getting hit, most people will still respect such situations.

It really is as it looks. Yeah it's difficult but muscle memory starts to take over. I'm pretty decent at this gem loop and my strategy is to use the A and C crystals alternatively. If I put out an A crystal, I'll start off with 2A2B and if I start with a C crystal, 2C2B. Most time I hold the A or C at the start of the string to prep my next crystal. The duration of the 2B and usually a 5BB to follow up and detonate a high cystal gives me plenty of time to charge the crystals and keep the loop going. Becareful though because there are holes in the loop especially if you have microdelays. Sometimes if helps if the opponent is too eager to be offensive, but if they are overly defensive, you eventually wanna charge partition a Bdrill into a low crystal.