It's good airmanship to notify cabin crew/pax as well of what you're about to do.
What? You have to be kidding? This is a waste of time and effort. There really is no need to inform the passengers about "normal" techniques and I'd be really reluctant to tell them about abnormals unless they are so strange they might wonder what you are up to. And most cabin crew know what is and what is not normal.
PM