Difference in individual bird personalities and species make every experience different, I think. Agree with juvenile roost. I have guineas, so that may be the species difference- I put my juvy roosts higher and closer to the wall-plenty of room for a keet, but grown goons have no interest.
The 1st time I integrated, I cut a doorway big enough for the keets into the brooder and moved the whole thing into the coop, tucked under the drop boards. The keets stayed in it for a cpl of days and then started venturing out, knowing they could duck back to safety of brooder.(large tote). So now I have an outdoor brooder and made an new indoor one.
The last two batches of incubated keets, my hen was broody so not part of the equation. And again, this may be diff in species that won't work for chickens.

The guineas always come to patio door to see what's going on in their old house. I moved the brooder infront of the door every a.m. -another diff, bc it was summer.
The little ones could look out to the big new world, and the adults would come peak at the "nursery".
As the days went by, my boys were spending more and more time watching the keets through the window, and when they were big enough, I started taking them outside for short excursions in an enclosed mesh basket.
Long story short, the first time I took them out w/o the basket, they went from my arm straight to the males,& after that, I no longer existed. The males lined them up, protected them,disciplined them, and in the coop they went.
When the hen moved back in w/her brood, she wasn't as welcoming. But they had those roosts and as long as they stayed away from her and her keets, they were fine. Not that they always did, bc everyone wants a mama-but it worked out.