Thanks so much for this info and the dipping pics, really helpful. I thought I just had a problem with too much preening or a rooster being a bit rough, until the hen with the bald patch really got bald ( most of the feathers on her back gone and on the sides of the patch, feathers broken off) Going to start with olive oil until I can get some sulphur. I have only ever seen it in powder form here, perhaps i can make a paste or also just dip her. Thanks again.
You can also take the powdered sulfur and put it in a panty hose stocking, tie it off and use that to dust them like people do with Sevin or Permethrin. Hang them upside down and dust under wings, around vent area and along front and back. Just make sure that whatever kind of sulfur you work with to wear clothes you don't mind having the permanent smell of sulfur!