Here in the PNW, we have slugs the size of Hollywood dogs - and lots of them. They will tear your cabbage apart and feast on other leafy veggies as well, including ripe tomatoes (they don't bother green ones, only the picture perfect "was going to pick that one today" variety).
I tried Slug-go with moderate success but it washes away easily with rain or watering and some get through.
Midnight hunts are effective but who wants to go out every night for months on end?
Placing items they can hide under during the day, then flipping them over and killing them works ok.
Plates of beer or water they drown in will take a few also.
Copper barriers seem expensive and not practical for larger gardens.
Anybody have another method that works well?