How to relieve pain from tendonitis in the elbows?

My hubby has really bad pain from tendonitis in his elbow. He takes Advil and puts a arm brace on it. But he is in so much pain and can’t get it relieve at all. Anyone have any suggestions or tips on what to do? Do you know if he is supposed to use hot / or cold?
I know you are supposed to rest it and let it heal, but with his work, he cannot take that time off. He has to work, and he uses it a lot at work. HELP!!! How long til it’ll go away?