the guafenesin or Mucinex is what I take for that. I can really tell that it helps with the thinning and being able to cough it up. If he had radiation to the head and neck, (I did) and the saliva glands are damaged he will be thicker too. I can't say about the breath other than to check and make sure all the teeth are good. My teeth were destroyed by the radiation and gave me bad breath until I had them removed.
Hope you find the solution, ask your dr. as always.