Hi Maureen
Welcome to this excellent place for info and support!
I have just finished similar treatment but only had radio once daily so it might be quite different in outcome. The side effects i had were all thrown in together ie it's hard to tell pain from burning of tongue and throat, thrush or inflammation generally. Either way, the burns along tongue are still giving me grief after 9 weeks so expect a long haul! From what i gather, thrush comes and goes but if your husband takes the wash as a precaution that's all he can do. I was advised to eat natural yoghurts to try and get the bacteria rebalanced in there - tasted grim but might have done the trick!
For me the best way of maintaining oral hygiene was to constantly flush with bicarb/salt solution, made warm and forced through a monojet syringe. I gargle and flush as often as possible which prevents having to swallow green gunk that causes sickness, it also relieves the sting considerably. My real godsend came in the form of a dentist's suction pump that i carry around to remove all the thick saliva. I was overwhelmed with copious amounts of the stuff but sucking it away with that is a joy - painless and easy, instead of needind a spitoon all the time - maybe your husband hasn't developed all that yet but it may come!
Hope this is of some help to you both, good luck and keep us posted, best wishes,
Frances