I don't know how well this photo will show what we did to get 15 pullets and 14 hens used to each other, but...
We used two strips of plastic deer netting connected with tie wraps to create a large curtain that divides the run. The pullets in the center of the photo are on the far side of the curtain. The rest of the run and the part that provides access to the coop and yard, is accessible only to the hens once the curtain is down. About 1 foot of the curtain drapes on the ground and I set 2' sections of rebar on there to keep it in place; it's not like they try to barge through it. I stapled one edge to an 8' long lath and velcroed the lath to the building; that's the "permanent" side. The other side, where I come and go to feed/treat/water/sit with them, attaches to one of the structural 4 x 4 uprights via little hooks screwed into the upright. The netting easily slips right over the hooks and is easy to connect and disconnect from both sides. I reinforced the top and sides of the netting by weaving some thin cotton rope through the little squares of the mesh, and that gives the whole curtain a little more structure. Inside the coop I built another temporary, smaller coop for the pullets out of 2 x 4s and more deer netting. The hens have the run of the rest of the coop. The arrangement takes some wrangling of the two groups: In the morning I let the hens out into the run and they follow me to the yard for some scrambled eggs. I lock them out there, then open the pullet coop. By now they know enough to run into their section, where they get scrambled eggs, too. Once they're all corralled there I drop the curtain (it holds up out of the way with a tiny bungee while they're in transit), set the rebar on it, and let the hens back in so they have nest box access. At night it's the same thing: hens to the yard, pullets to their coop, hens back in to their coop. This has been the arrangement for over a month, and before that the chicks were confined to their coop, but still in full sight of the hens. They've been exposed to each other without physical contact for at least two months now. Last week they started getting short supervised visits with the curtain up. The hens haven't bothered the pullets excessively, but I still wouldn't trust them alone with each other for extended periods. The pullets don't want any trouble, but I also don't want them picked on, so we're going very slowly until I can trust them not to be murdered by the hens.