It really works! As I explained in a previous post, my burdock plants were being chewed to the nub by snails. As soon as a new leaf would appear it would be chewed off by the next day. I applied a heavy layer of oat bran, and as you can see in the photo, they are winning the fight!
Oat bran still works when it rains. If you overhead water you just have to be careful not to wash it away . . .