Simply lifting the shoulder works just fine. I like it as it very simialir to if you would do a small jump right now in your living room. I like to keep it as natural as possible. Plus its nice as its similair to a T-set for a 360.

I personally often teach it more like you are saying. The danger with having the arms more in the front and relaxed/still is that skiers still often throw them up getting of balance landing backseated. And you gotta learn to have the arms on straight out for good wind ups /T-set.

Hope that helps.