I also had some slug and snail problems in my hostas. Had handpicked the bigger ones, then sprinkled table salt on them. My hubby thinks I am too harsh on the critters, but they really can demolish my hostas, and other plants. I always do spot inspection in my garden especially when it seems cool and damp. I guess once you have these critters, even if you catch most of them, they have already put some newbie eggs in the soil and sure enough, something will be munching on the poor leaves.
I have just also started putting finely crushed eggshells around the plants and some leftover coffee beans, keeping fingers crossed that it will help somehow. Well it is now late spring, and as it goes warmer, hopefully a lot less of these slimy critters..