Jim Stone discusses the hand-ball contact and release for setters. Right before contact, the hands should be shaped to the ball - like a basket. During the release, the thumbs should turn inwards to flick the ball forward. Keep the shape of the hands throughout the contact and follow through fully.
With a backset, the hand position should stay the same. The only change is that the hands should make a flatter angle so the player can lift the pull backwards. During the follow through for the backset, hands should still follow through.