I did some salt water mix thing and it was very salty, and I gargled with it 3 times a day, and my canker sore just got BIGGER the next day. I've tried other medicines for it and they don't work at all either.
That will help keep it clean, but if you want to get rid of it, you should use Baking Soda! It will burn for a minute, but it will kill the sore. Leave it on there for like 20-30 seconds. then rinse with water and spit!