1. First off do the Crabwalk/Roadie Run Glitch
[see Crabwalk tut]

2. You have to get to an elevated stairway and an object to roll into, and be sure not to take cover.

3. You should be walking into the wall because it is pulling you back to where you started the crabwalk.

4. Once you are able to roll your controls for rolling will be screwed up so you have to roll to the top of the stairs you want to airwalk on.

5. Now your character will walk on air until he hits an obstacle.

And there you have it, you're a real magician you can walk on air!