How often have you heard that teamwork and eye contact were important? Eye contact allows the whole referee crew to be on the same page.
In the video below, a seemingly easy goal kick or corner kick decision is being made. The ball gets crossed from the AR side an goes out on the referee side. Two players, one from each team, challenges for the ball, making it unclear for the AR who touched the ball last. The referee takes initiative and signals. But just in case his AR has different information, he briefly looks at his AR.
This is all you need. A quick look at your AR will help you make sure that your AR is following your signal or your AR has the same information with you. Otherwise what would happen if your AR has information you did not know about? It can easily lead to two people signaling for two different restarts.