I highly recommend this method, especially as I did have a rough experience with my first introduction of 4 hens with flock of 2, where 1 hen got spooked and ran into the AC unit killing it instantly. I highly recommend you keep the barrier up until the flock starts to ignore and show less interest in the new birds and open yard so much better so new birds have room to run and not get cornered and less risk of running into objects, like the coop, etc and cause injury.
I actually found a picture I took of barrier splitting my enclosure up with a new group of girls that I sent to neighbor that was going to watch them for a weekend.
Old window screens or a makeshift tractor (I made one from PVC pipe, irrigation tubes, and bird netting with zip ties and some screens; see top right picture of last picture) work great to separate new and old hens, especially as loose chicken wire can be hard to set up temporarily as it flimsy and wants to curl.
I actually found a picture I took of barrier splitting my enclosure up with a new group of girls that I sent to neighbor that was going to watch them for a weekend.
