I've had pretty good luck with this method. I put the new gals, in a large pet carrier with wire door and sides (so they can see each other) into the coop at dusk, when everyone else is in. In the morning (not first thing) when I let them out I make EVERYONE from the old flock go out, and then block the door with hardware cloth. I have plenty of food and water, and a nest box outside the main coop as well as inside. Then I let the new gals out to explore their coop, but they can't get out into the yard, The old gals will come to the door and look in at them. Toward dusk I get in the coop and put the new gals back in their carrier, and take away the door so the old ones can come in. After a day or two of this, I'll try to let the old gals in a bit early, with the new ones still loose, but the pet carrier is still in the coop and open. The new ones will probably hide in the carrier. If some of the old ones ones try to go in and peck them, you may need to close the door of the carrier. By the 3rd day, let everyone out in the yard, with access to the coop too. New ones will travel together but will come back to the coop and into the carrier. Again, if you find that old ones are going into the coop in the evening to beat up on them, close the carrier door at night. By the 4th day, you won't need to do that, and some of the new ones may decide to roost on the roost and not in the carrier! By the time none of the new ones are going into the carrier at night, you can remove it (though they may still be using it as a nest box). Whoever is lowest on the totem pole at that point may roost in a nest box for safety, but let her. In a month they will be one flock. I've not seen much blood this way.