Putting your hand out with an index finger raised also works pretty well, and might be less socially surprising. You can also vary the details to send different messages, with “arm out and index finger pointing just above the person’s head” being “stop talking right now!”
Putting your hand out with an index finger raised also works pretty well, and might be less socially surprising. You can also vary the details to send different messages, with “arm out and index finger pointing just above the person’s head” being “stop talking right now!”