Intros are always hard! My top take aways from my experience…
1 - look don’t touch should happen for at least a couple days. I bring mine out in the dog kennel and plop them in the run for the day
2 - make sure when you let them free that they have a place to run and hide and do the intros supervised.
3 - there will be pecking and some fighting. They have to establish that the newbies are at the bottom. Sometimes it can get mean and they gang up on one that’s meeker—so that’s when I end the session and try again the next day.
4 - if they can go a whole day with no drama, I help coop them that night. If after a bit I find them all huddled in a corner or their kennel, I bring them inside to sleep. I tried the “coop them at night and in the morning they will all be buddies” and it did not work. The morning when they are all full of saucy energy is not great for newbies.
5 - flock personality matters a lot. My bantam run is really easy to integrate newbies and littles. They accept new ones quite willingly. My big chicken flock takes more effort, they aren’t quite as willing haha.
6 - sometimes your sweetest chickens are the meanest to newbies. They don’t want to stay at the bottom of the pecking order—so they can get a bit relentless to the new ones. So watch for that
Good luck!! I hope they get along great!