The reason instructors won't teach you is probably either because they've seen your ability already and don't want to say "You're not at the required level yet, you need to work on other things first" or it's not something they often teach, so they are unfamiliar with a progression they can use to teach you.
In reality, these types of maneuvers come from experience and understanding of how a board moves on snow in relation to the movements you make.
I'm not sure if I fully understand what you're after but here's a small progression you could use:
Practice super fast speed checks on the flat ground, but let the heel edge engage and carry you in a new direction. Slowly progress it to side banks, by riding up on a low angle, then turning and let the board ride back down the fall line on your heel edge. As you start to get it steeper you will need to skid/slide the first 90+desgrees of the turn by turning you upper body into the turn first and then letting your legs snap back round underneath you following your upper body.
The steeper the hill the more aggressive the turn needs to be, and eventually, as you've already been told, once you're going at a high angle up the hill you'll find you will need to lean backwards down the hill - you can think about dragging your rear hand if it help.
Possibly the best way to learn these types of things is by watching others and trying to mimic their movements as well. Where abouts do you currently ride?
Last edited by nzshred; 02-25-2013 at 12:34 AM.