Actually it's the same method as in s3, just a quick flick/rotation.

With s2 just use the trigger, slightly press and once in a nose/tail do a nollie or ollie while positioning your left thumb stick. It's not that hard really... you can also do them without the ade of triggers for even smoother looking. (take mastering )

S3 trigger will not work because of the way hardcore mode works. you can't bounce if that makes sense.

Also what Saunders said works too, but it limits you to that one object but is a good way to practice rotation/timing though.

I can show you some examples.. montage!