So I've been practising shaving without looking in the mirror. As I don't wear my glasses when I shave, this ends up looking much the same as when I shave and still look in the mirror.
I'm testing the theory that you can shave by sound and system. 'System' means doing things in the right order, with special attention to the chin and the left upper side of the lip (for right-handers, which I am). 'Sound' means that when you hear 'rasp, rasp, rasp', you keep shaving, and when you don't, you stop.