During my time with the USAF many moons ago I used to enjoy the procedure whereby an aircrew audience being bullsh*tted would pull out one end of their flying scarves and flap them gently. This was known as 'waving the bullsh*t flag' and would invariably return the bullsh*tter to his seat. Another procedure was shouting 'the hook' (taken from a TV comedy show, I think) and a long hook would reach out from stage left to remove the bullsh*tter by the neck. These would both work well at PMQs, I feel.