My old squad had eight basic hand signals we drilled weekly. It feels silly until your radio dies in heavy brush, then it's all you've got. That visual layer is what keeps a bad situation from going completely dark.
Remember that panic when comms cut out mid-move? We had a simple one for "stop" - closed fist held up high. Another was tapping your helmet twice to say "listen up." It wasn't fancy, but knowing just those few signs kept everyone from scattering when the chatter went dead.