I can help you. I am Deaf plus State Ceritifed Firefighter-1.
The Best thing you need to do with him to establish a communcation with him. Train him and have him teach you sign language on the tools name, equipment name and ask him information about sign language like preconnect 1 hose line, so when you tell him a order, you need to show him a sign language that he has taught you and he will get the tools out by your order.
Any Question? Please feel free to ask me anything.
I m a Volunteer Firefighter with a Certified State FF-1, Farmedic, Pumper Ops and hold many more certification. I have fought several strucutal fires. I am deaf, but no speech impairment.