You can wet the slugs whistle my making a beer trap which will together with hand picking and sprinkiling diamtomaceous earth, will get a handle on the slugs.
Hostas love moist soil and I would keep good growing conditions for it as a first priority since it is sustaining leaf damage.

Unfortunately, slugs and snails like hostas. Some of the thick-leaved varieties are a little less tasty.
Keep the ground conditions moist for healthy plants and be prepared to go out in the evenings and pick off slugs and snails from all plants, not just the hostas.
A good layer of sharp grit around your hostas - larger than the spread of the plant - will help as well.
In the rest of your garden keep things tidy and clear up any debris where slugs and snails can hide.
Empty grapefruit shells turned upside down make good traps and beer traps are ok if you have a regular supply of free beer (make friends at the local pub and get them to collect the slops for you) but pretty disgusting to empty.