i have had a very annoying ulcer that was in my mouth for longer than it should be ( about a week and a half) and ive also tried gels and such but then i found out about trying brown sugar
before you sleep in about an hour, take a pinch of brown sugar on your finger and press it into the ulcer for about 20 seconds or something(it will be slightly painful). no need to rinse itll melt in your mouth.
right before you sleep after you wash your teeth do it again. In the morning if it still hurts a bit do it again.
by the afternoon you wont feel anything! it would still be there but it wont be painful. it worked for me.
what happens is that the brown sugar sort of absorbs all the acid in the ulcer, cleaning it.
so thats one solution.