Put it as the first reaction after a questionable line in a cut, then follow it with the bruh sound if the moment needs a second verdict from someone else in the scene.
關於此聲音
A one-second clip of Sulley letting out a low, drawn-out mmm groan, with no words around it. It lands as doubtful and mildly annoyed, like he has heard the plan and does not buy it at all. The character is James P. Sullivan from Pixar's Monsters, Inc.