I used PetSmart cups since they float the best and don't have stickers on them like PetCo does and I acclimated them to the tank water so that I could just scoop a new cup with tank water, take one girl out and put her in that cup. Then her old water goes down the drain/bucket so as not to contaminate the tank water if she is sick. I would do this daily/every other day and you can go three day's without a change but every other day is preferable. And then when deemed not sick, try to get the majority of them in and observe.
If you find that one female is being down right ruthless, put her in time out in something mostly clear, floating in the tank that she can't get out of so that she can still see the girl's but not hurt anyone. You can keep her separated for another two weeks or until she calms down; release her and observe. If she's still ruthless, she may need her own tank or try a time out again and see if that helps any.