Train them to a treat bowl - works like a charm! Find a dish, I use an old plastic "untippable" dog dish. I put their favorite treats in that dish, and offer them during the day. A few times a day, a small treat of something they love like yogurt, mashed bananas, tomatoes, etc. - Move the treat dish closer to the coop. Then, put the treat dish INSIDE the coop. When they're used to going in, just put the treat dish inside at dusk. Do this for SEVERAL days in a row, and eventually it will become a habit for them to come inside at dusk, and you can stop with the treats then. I also say "chick! chick! chick!" when I put the bowl down, so they also come running to just the sound of me saying that eventually, as well. Good luck!