I switched coops too. Here is my story on my experiences putting my pullets with my hens. First I let them all out in the yard together when the pullets were about 12 weeks old and the hens were about 1 1/2 yrs old. I put lots of scratch out for them. It didn't go to well. The hens chased and picked on the pullets terrible so I separated them. They had been in different coops and adjacent runs for over a month prior to the first time I tried to put them together to range. Prior to putting the pullets in a coop, they were in a chicken tractor which was next to the hen's run and yard since they were chicks.
Every evening for a month, I would take some scratch/seeds/grain mix and sprinkle it in the feed, and on the floor of the coop that I wanted the birds in. I was training them to go into their coops at night. The two coops with adjacent runs had access to a fenced in yard. I put a second pop door into the hen's house so when I eventually put them all together the pullets would have another door to use if needed. Also I had nest boxes in both coops. When I put them together in their yard the last time when the pullets were about 20 weeks, I had two hens that were terrible and jumping on the pullets and pulling their feathers out. I took the two most aggressive hens out and separated them from the rest. They were put into a separate pen for a week where all the rest of the chickens could walk around them see them but couldn't touch. When I did let them out, I put them all together in their yard with plenty of treats and scratch out hopefully to distract them. It worked for the most part, but for one of the hens. She was still very aggressive. When I saw her jump on one of the pullets I put her back in jail for a couple of days then let her out. She was still somewhat aggressive. When I saw her jump on a pullet, I sprayed her with water from a hose which is next to the coop which caught her by surprise. She went running into the coop and didn't come out for awhile. I have repeated the hose caper a few times. She has calmed down since then.
Since my goal was to eventually get all of the birds to live in one coop, I decided to switch the birds around and put the pullets in the hen's house and the hens in the pullet's coop. I shut the runs off from each other and the yard so they only had access to the coops and runs I put them in. I didn't lock them in the coop. I left the pop doors open to the run for that coop. They could go at free will into their run but not the other run, other coop or their yard for a week. I continued with the treats in the coops in the evenings trying to keep the ritual of evening treats in the coop so they would go in for their treats. After the switch for a week I opened the gates to the runs and yard. I let them all range together. For the next week I let them choose which coop to roost in and most except for 3/4 birds roosted in the hen's house. After a week of free choice coops I shut the pop door on the pullets coop. Now they either had to roost in the hens house or in the run. They do have a ladder in their run. There was a little bickering in the beginning at roosting time but all is well now and they have worked out their pecking order. They all roost now in the hen's house. I don't know if my story will help you in any way. I know every integration/combining of flock are all different and unique.
Sorry this post is so lengthy.
