Put it at the very end of a scene, after the other person has already been told to leave once, so it acts as the final word. Let No No Wait Wait play just before it for a pleading reply, then follow the dismissal with Nelson's Ha-Ha! to underline the joke.
À propos de ce son
This is a short spoken clip in Portuguese, lasting about 1.4 seconds, in which a voice repeats 'Vai' before telling someone to go away and finishing with 'Xau'. The delivery is blunt and abrupt, turning a simple goodbye into a comic shove out the door. It feels playful rather than angry, like a friend jokingly cutting a conversation short.