Might just be cus we're both neurodivergent, but we have a lot of non verbal cues, though he's nowhere near as showy as I am.

Whenever I end up overstimmed and go non-verbal, I tug at his shirt gently, or paw at him. From then it's simple ASL. For him, he genuinely just has simple phrasing or wordings that are kind of "key words" between us. The both of us are high functioning in our 20s, this is just kind of how it ended up and we're both super not subtle about it. It's great.

Edit: we literally do pigeon noises at each other at random. One of us says coo and the other goes roo. It's literally just a "thing" between us and it started because of us watching pigeons together and it stuck.