Go in well after full dark and take the pullets out of the nests, get your hands over their wings so they don't flap them, and carefully place them on a roost.
Place their feet firmly on the roost and hold them for a second until they are steady, then release the wings and put your hand on their backs until they settle, shouldn't take more than 10-15 seconds.
I wear a headlight set on low, just enough for me to see, but keep it pointed up rather than on the bird unless absolutely necessary.
You might have to do this every night for a week or so.
My experience was that I had some pullets that the older birds wouldn't let roost with them so the pullets wanted to roost in the nests. I put up another roost just a couple inches lower than the main roost and began removing the pullets from the nests after dark and putting them on their roost. Did that for a couple nights, then started going in at dusk and poking them in butt if they got into the nests(I have 'outside the coop' access to my nests boxes so this was easy). Pretty soon all I had to do was walk in and they would leave the nest and go to the roost so they didn't get poked in the butt. Took about 3 weeks total before they got in the habit of always roosting on the roosts instead of in the nests.
I had this problem with one hen who, not coincidentally, is at the bottom of the pecking order. I figured she was getting bullied a bit up on the roosting board.
I would go out every day an hour or two before sunset and block off the nesting boxes with a slab of plywood. I would then come by after sunset and quietly remove the plywood so the hens can lay early in the morning. I could see she was now not roosting up on the top roosting board, but a foot down on the edge of the poop-board support beam. That's good enough and she goes there on her own now.