Not completely Assetto Corsa related, the gestures obviously cant be made but you can communicate by in game chat or preferred Discord. One does not simply jump into tandem with other cars and drift straight into their doors, there is a method to the madness. You need to make sure any drifting you do with other drivers is planned and well understood by all parties, as this is potentially dangerous and ruinous to the cars involved (even tho in AC they are virtual lets pretend they are real lol).
Would you want some random idiot crashing into you when you have no idea someone is even on track with you? Also, it is super important to always be aware of your surroundings, have clear and simple communication skills with other drifters, and have fun. That about covers it, watch the video and don’t be an idiot! (we are all idiots, I know, but try not to be a complete one).