Salt water is good - but only 1/2 tsp in a full 8 oz of water - if you make it too concentrated, it will irritate more than help.
Amosan is a good product as well - comes in little sachets that you mix with water to use as a rinse.
Kaopectate/Benadryl 50:50 helps for some.
Avoiding caffeine, chocolate and spicy foods is important as these foods will irritate the cankers.