Suggestions for combining my birds?

[537264]

I have 3 Barred Rock hens, 2-3 years old. I also have 5 Buff Orpington pullets that are 10 weeks old.
The BR were moved into a smaller pen and coop and the BO are in their old, larger pen and coop. The pens are next to each other.
I want to put all the birds into one coop and pen when the BO are 20 weeks old. I only have electricity to the old coop, and I have an automatic door and heating in that coop. So for convenience I want them all together, especially over the winter.
What is the best way to put the old hens in with the younger ones? I anyone has done this before I would be interested in hearing how you did it and how it went.

 

[Mamatomany123]

I've never waited until they were older but I have integrated chicks in with older hens 3 times. A see but no touch setup for a few weeks. Heres how I set up my chicks in the run. By 2.5 weeks they were fully integrated and had hide out spots that the big ones couldnt get in. Of course you wont be able to do that now since the younger ones are big but I think a see but no touch will work.