Nose pinching is my favourite technique. It rarely fails, although, sometimes I have to do it more than once, because breathing through a pinched nose is an odd sensation. I like to make sure I'm pinching properly, the second time (trick: still expect to breathe. If you expect to not breathe, you won't breathe. You have to expect the check to pass).
Plus, if you pinch your nose, while awake, no one seems to question it. I have done fully watched nose pinches... on transit, around classmates, even when directly talking to people. No one ever says anything.