As a finisher, JJ was good at jumping off two feet and square. Rarely got shots blocked and was able to adjust in air as a result
He didn't have a great left hand, but it didn't matter. His shot got defenders close to him, so a quick first step or attacking closeouts on the left side meant he could get to an inside-hand finish
Everything comes down to FOOTWORK. Pre-catch, his footwork would allow him to catch it on his left and rise quickly.
His hip-turn is elite. Those are traits of great shooters. If guys want to work on something fluidly for their body, try to open up and loosen their hips. If they can, then teach aligning right hip to the rim