I don't think I get more than is usual for a normal person, but I use Cankaid (I think you can find it in the dental hygiene section). It tastes kind of bad, but you don't have to use much. Just put a drop or two directly on the sore. It's main ingredient is peroxcide, so you can probably use that in lieu of it for the same effect. The Cankaid is kind of syrupy, so it sticks to the canker for longer than a peroxcide wash would, so if you use peroxcide, rise with it several times a day. You can use the Cankaid once or twice a day (I put it on at night) and you will notice that the sore will go down a lot in size overnight.
If you get a cold sore on the outside of your mouth, try Carmex. That stuff is great at healing up small sores. I have even put it on my face when I have made a raw place trying to get rid of a pimple. It will heal it right up.