Apparently my left eyebrow goes up all by itself and the ‘look’ is enough to freeze anyone at several paces…not my words I might add but I’ve found it an effective way of getting people to shut up.
You say “chut” which you pronounce almost like shütttt.
And you glare (and if you like you can be dramatic and use two fingers to point at your eyes then at them and maybe then draw your hand over your throat while rolling your eyes back in your head … ) but “chut” will do fine.