Mine usually will go into the coop by themselves when it starts to get dark, but before they had matured, they were all locked in there for weeks without getting to go outside. We feed them inside also, so when they hear the sound of the tin trash can we keep the feed in, they run in, and if they hear me opening the door to go in, they run in. Our coop has a human door, an inside part the chickens don't have access too, a smaller part for our chicks, and the larger part with nesting boxes and a roost. Usually by the time they all hear the first door opening, the trash can opening, and the second door to gain access to the part of the coop they go in opening, they are all safely inside. Mine get fed table scraps and free range, but the only time they get fed their actual feed is when they go in at night. I've never had issues getting any of them to go in, even when it's still daylight and they hadn't started to go on their own yet.
I can also get mine to come to me, in the coop or not, just by yelling "Chickens!" because I often will yell at them when I feed them either their feed or table scrap treats. Food is the easiest way I have found to train any animal, chickens included.
