Depending on the plane, it can be child pay, or it may take a little finesse work.
Like Ken mentioned, key is to have both wings completely stalled: the most common issue I see with people learning to harrier, is the "fear" of throwing full elevator when going slow, although it is the way to get a stable and predictable harrier.
Wing rock, besides possible wind gusts or external factors making it difficult, comes from the wings"un-stalling".
The Edges are probably the easiest to harrier. Your 100cc Extra takes a little more finesse, but can do some other things better.