the basic dynamics of turning that steep is that as you increase speed your lean angle for the turn increases. Hence to keep the turn you have to lean in more. Ultimately to go faster its a balance between your lean angle and your speed and the angle of the turn. Ofcourse in all this you still have to be looking to where you're going or you will crash. THe bike follows where your seeing.
Getting your knee down is only for the tracks. I am so reluctant to do it on the streets, ofcourse i wouldnt do it on mine only because its a bitch to bring it back up, i hate when i have to do a quick S turn at high speed, cause im going from one side to another in quick succession. Mind you these riders are in really fscking good form to do that, and unforunately im not.
In anycase you pick up how to get your knee down when you do a track day and you start slowly getting the hang of taking turns faster and faster.