I want to share my experience with the last integration I am currently doing. I have had chickens for 4 years and always had done integrations the "old way" waiting for the chicks to get big enough to defend themselves and keeping them in a separate pen for many weeks. This time I wanted to try something different and after reading Azygous posts and article I was very encouraged to integrate earlier.
This is the pen where I have my 2 pullets. It is a 10x20 kennel, it has a 6x8 coop and a separated nesting coop.
I moved the chicks when they were almost three weeks old, I put them in a dog cage 4x4 with a Brinsea 20 heater, waterers and feeders. I also made a portal 5x7 and painted it red so the chicks could find it easily.
Azygous has been a very big help with advise and has taken me thru the process very nicely (I was a nervous wreck). She recommended to add more portals because the chicks tend to freak out and don't find the safe way to get away from the pullets.
So I improvised and added two more portals.
I left the chicks out after two weeks of being in their new home without the pullets being around. They had an outing of about an hour every day for 4 days. I wanted them to learn where the portals were and their way around the run.
After 4 days, the "fun" started. I let them out with the pullets and there was a lot of chasing around, jumping and flying all over the place. At the beginning it was chaos but I let them be and watched for a while until I put them back in the cage. As Azygous said, they learned where the doors are and now they come and go as they please. The pullets still chase them but they now run straight to the portals.
Obviously they are not integrated yet but at this point I am glad they are moving around enjoying more space and running. They discovered the automatic door that takes them out in the yard where they can eat bugs and grass.
I plan to continue with this set up until I see the pullets are not so aggressive, then I will try placing them in the coop at night to roost.
I want to give lots of credit to Azygous, if it wasn't for her article and experience she has posted in the forum, I would not have tried this method of integration.