Both of my dogs are trained with hand signals, to practice I sometimes don't say anything and only use the hands.
Make up your own, and use what feels comfortable to use.
For example,
For down I have Palm down and I lower my hand.
Sit I have my hand in a fist facing down.
Stay I just hold up my hand with my palm facing their faces.
I have wait: hold up one finger.
and so on
Best of luck to you!!