Sounds to me like Madeline's 'cure' is the best so far.
Used to have a lot of experience with mouth ulcers (boy, was I a wreck in my twenties, mouth ulcers, coldsores....

)
My best tip would be for 'Chloraseptic' Spray. Apply it before you eat ('cos that's the worst thing, isn't it?)...and you can go and eat a tomato, no trouble at all.
It used to be very cheap years ago...you'd get a big bottle for about £3. Gradually the bottles got smaller, and more expensive, but it's still worth buying.
The idea of biting them is making me feel quite ill...