You are on the right track. I hate artificial lights in brooders and coops.....it trashes their natural day/night cycles and leads to overeating just at the time their tiny digestive systems are beginning to mature. Temperature guidelines are outdated and in many cases dangerous. Chicks do far better getting cooled then hustling back for a quick warmup, totally self regulating - before we realize it, they’re back out learning about their world.
I often wonder - if a 2 pound hen can do it with no books and no experts, why do we do it so differently and think we are doing it better? Brooding outdoors among the adults is exactly what she would do so that’s exactly what I do. Otherwise we’re raising spoiled divas, while she raises sound families ....no nightlights under her wings, no forays out every couple of hours during the night to eat and drink, and they thrive because that’s how their little bodies are geared to work and grow optimally. They’re rested, calm, and confident that they can be big chickens too. They have the courage to explore every bit of their environment - which includes us - because they always know where safety is if they need it. They eat dirt (getting natural grit, microbes, and fungi in the process) and chow down on chicken poop and weeds and any larger tidbits mom finds for them. That build up natural immunities.
She’s not taking apples away, coring, peeling and chopping them before she lets them have them. She’s not checking goodies they find for germs or dirt before they eat it. And she’s not parked in one place as she dust bathes and forages....they have to learn how to find her if they need a snuggle. The only difference is that Mama Heating Pad is stationary. Mama Broody is not. I raised one batch of chicks using the conventional methods, then dumped that whole program and imitated a broody hen for the next 8 batches. I wasn’t stressed, the chicks weren’t stressed, and the adults weren’t stressed. Chicks were basically on the lowest setting for a few days by 3 weeks and integration was started then, then the Pad was turned off the beginning of the 4th week, they were mingling all day long with the Bigs, and midway through that 4th week the entire brooder was taken out and they were fully integrated with the flock. Every batch. Every time. And I should mention that Sprigtime “chick raising” temps here are in the 20s, sometimes dropping into the teens with high winds and sideways blowing snow.
So worry less about the lights - turn them off as the sun goes down. Even better, turn them off before sundown and let them go to bed in that dusky twilight all on their own, since they’re preprogrammed for that.