Here's something that my husband did during the worst of the radiation (and a month or so after) that really helped. We took some cotton cloths and got them wet and soaked them with some Tom's mouthwash (natural, no alcohol spearmint mouthwash). He kept them in a plastic bag in the refrigerator (or a cooler when he was out and about) and used them to gently wipe his mouth out when the mucous would get bad. Really helped relieve the mucous and also helped with the pain from the sores. Of course, he would keep them very clean. But both the ENT and the oncologist are now suggesting this to patients.

Best of luck to Eric (and to you...it is so hard to watch someone go through such a difficult thing).
Anita