Jason Scully is a really good teacher (and don't let all the online marketing fool you). I don't know the guy, but I know that for sure. How? Because, I'm probably one of the very worst black belt teachers in BJJ. So, I know bad teaching when I see it, and Scully don't got any.
What makes a great BJJ instructor? To start, knowledge and capability. Of course. They've got to be highly skilled and they must walk-the-walk, as it were. But, equally important (and this is where I don't come in), a good instructor needs to be able to precisely break down technique in such a way that students understand it and can emulate and reproduce it. Without that, there is no good teaching.
For years, I didn't care one bit about teaching BJJ and the skills and patience that go in to it. I only cared about my training and getting my daily fill of battles and subs. You get the picture. The skills behind instructing well are invaluable for all of us. Heed my warning, grapplers, and start learning how to teach peers and lower belts now. Otherwise, you'll end up like me, only without the good looks and badass BJJ/grappling website.
Jason Scully. He's a really good teacher. Now, watch him go over some of the finer points of an effective and complete guard pass. Basic stuff, but very well communicated by Scully. Learn some stuff.