Kuhlies will not eat snails. You actually want botias for that. Botias are often called loaches at LFS's. Skunk loachs (botia) or clown loaches are really great for eliminating snails - they are amazingly effective and it is their favorite food. But they are a schooling fish so you need to get multiples.
I've found that it's best to get the smallest ones you can find, the younger they are, the hungrier they are. Once they start getting in the 3 inch size ranges they tend to be a little less motivated.
If you have a big infestation - just get a bunch of babies, and then when they get bigger, trade them in for smaller guys and keep doing it until the snail population is wiped out or where you want it to be.