The more normal birch rod was, by all accounts, extremely effective, but I have little knowledge to pass on to you, except that I have heard that, unlike the cane, the first few strokes do not seem to hurt very much, but the intensity of the effect then increases dramatically with each stroke.
Does anyone remember way back in 1978 a lengthy piece on Newsnight about the IOM Birch? A policeman was shown hefting a bundle of four foot rods and then lashing it into a heavy leather chair. The chair jumped across the floor as a result. The next edit showed lady supporters of the birch talking about it and saying that it was nothing, just a gentle tap!