If you want to save effort, just make the brooder larger and leave the lamp at the "night" level. As long as the brooder has enough cool area, the chicks can move themselves away from the lamp in the daytime to avoid overheating. I find an oversized brooder to be much easier than than trying to fine tune the temperature in a smaller brooder.
(Note, this especially works well with a heat lamp, because the light attracts chicks to it when they are cold. An over-large brooder may not work as well with heat plates or mama heating pads, especially in the first days when the chicks are still learning what is where.)