Pain from radiation is likely to start at the end of the second week, start of third week. Your doctors should have prescribed pain meds for you. The rinse is a good idea as it helps to keep your mouth fresh. Do you have access to a dietitian at your hospital? He/she can advise you on what supplement you should be using. When I tried to buy Ensure for my husband at the pharmacy, I realized there were many different kinds and in fact my husband was on something that had to be specially ordered through the pharmacy. So, maybe it’s a good idea to check with either your doctor or your dietitian.