who is the best Kings Indian Attack player

You´ll also find quite a few games where Teimour Radjabov play KIA.

I could be wrong, but it seems most of the best players in the world will play the kings indian attack in blitz tournaments no problem, but its rare to see the same guys play it in long time control games. 

I always thought the guy was a genius. It's difficult to play like him.

A good introduction to the KIA is surprisingly Dvoretsky's book Opening Preparation.  It's only 2 chapters in a book that covers many other things, but it's a great two chapters on the KIA.

Maybe, it would be helpful to look at The King's Indian Attack Move by Move by GM Neil McDonald (2014).

With no intention to disrespect anyone, I don't have a high opinion.

I can't say much of the book, it's probably a very instructive book.

In terms of the most instructive player to follow, I'd recommend the games and analysis of Mark Dvoretsky. His articles on the KIA are better than any book I've seen on the opening.