Recovery for radiation to the throat is a slow process. Tell him not to get discouraged, it will come slowly. Mucinex is a great idea for the mucus. My friend had throat cancer and after radiation it took a good 3 months to really be able to eat.During the first 3 months, he had soup, mashed potatoes & eggs...whatever would go down.Taste also took a little while to come back. If he can't eat alot, have him supplement with boost, he needs calories for recovery.Depression is also very common.Maybe his doctor can prescribe something for him to help with this or maybe a cancer support group. It took my friend approx. a year to feel normal again. He is doing well now and is almost 2 years out of treatment although weight gain is slow.Be patient, I know it's hard at this point. Good luck & I hope this helps!