There's a product called "Kank-a" that is made by Blistex and ADA accepted.
I used to use it.....when I got them. I'd get really bad canker sores, or definitely worse than my mum or brother.
I'd get 3 or 4 at a time, and sometimes 2 of the 4 were really big. They'd be at maximum pain and irritation for around 7 days, and an additional 7 days if I accidentally, but completely involunarily, bit one.
I was digging through the internetz, and what I read was that in order to avoid getting canker sores, you need to find out exactly what was causing it. It could be anything, really. Anyway, it took me 22 years of being alive until I realized that it was acidic fruits/foods that did it. I cut out oranges (difficult to do), pineapple, lemons, and limes from my diet, and I think I've had a handful of canker sores over the past 6 years. I'll occasionally have a quarter of an orange or mandarin if someone else is willing to eat the other 3/4ths of it, but otherwise, I avoid them. I'll also have half a kiwi, or a few pieces of pineapple occasionally. I'll drink a quarter glass of orange juice to make myself happy.

Since oranges are my favourite fruit, it has been difficult. However, I don't punish myself by cutting those things out entirely.
Anyway, I'm not sure if the cause of your sores are the same as mine, but try it out. ANYTHING that causes irritation (i.e. mouth wash) isn't good for it. In my case, it would make it worse, since Listerine has the effect of, say, 1000 oranges.

When I use mouthwash, I need to use milder mouthwash.