I have OPL and BMS syndrome is certainly part of that whole thing. Initially, I thought the burning tongue was yeast (thrush). I looked for a mouth wash specifically for yeast but no luck there. My mouth was so dry (exacerbated by meds?) the burn worst so I drank a lot of water and took Diflucan (rx) which is an oral yeast treatment - just one pill every so often. I think it helped some. When I had a lot of ulcers in my mouth I swished with hydrogen peroxide which made a HUGE difference in the rate at which the ulcers healed. If it was really bad, I drenched a piece of gauze with the hydrogen peroxide and kept it in my mouth (between my teeth and gums) intermittently throughout the day. No one told me to do this but it dramatically cuts the healing time. When really unbearable, I have used Kanka to numb it. I also moved away from mint toothpaste and went with non-floride version which has helped incredibly (get enough fluoride from drinking water). I am not a doctor but since there are no definitive answers out there I have done a lot of research and trial and error things. So helpful to hear your efforts to address this demon. Thank you.
Btw... Oral Lichen Planos ( the mother of BMS) can effect other parts of your body. If it is limited to your mouth consider yourself blessed... It can change your life in ways too great to enumerate here. 🙁 No help to be found as of yet here in the US, the UK and New Zealand seem to have the corner on the market at this time but I have not given up hope. I can't give up. I will keep studying and digging. I refuse to believe that someone out there has not discovered a way to address this successfully. Keep you posted....