You want to work in the BF without too much molestation from the critters that live there?
1. Don't go at night. There are extra spawns of all mobs in every biome at night time.
2. First scout out the area and locate the Greydwarf nests which spawn them. Destroy them and any Greydwarves you come across.
3. It also pays to scout first because you can also locate the Skellie burrows/ruins and Troll caves. Don't work within earshot of those.
4. Go to work ;)