Oh please! Double-clutching has NOTHING to do with amplifying resources. I totally agree that engine breaking is the way to go and that using the brakes is a waste of energy. But double-clutching has nothing to do with either one. It is simply your preference on how to shift down. It adds no advantage to single-clutching when downshifting. In fact, all you're really doing is allowing the engine more time to drop in revs to better match the lower gear as you down shift. That can be done without double clutching.