Can I just add, this works great, but ONLY choose replacement roosters from the first 1/3 of the cockerels you removed. Some of the late-maturing group will end up huge and beautiful, but that puts late maturing genes in your flock.Rather than trying to pull the hens, it might be easier to pull the cockerels as you see them (combs bigger & redder), and after you've removed about 1/3 of the birds as probable-males, just feed the others the way you want to feed females. Of course you'd keep moving cockerels into the male-only group as they appear, but that way all females and some males would get a bit of feed restriction, rather than continuing to free-feed the whole group while you try to be sure about who the females are.
This is the first cull. If I haven't marked a bird as a rooster by 6 weeks, he's not staying, no matter what he looks like later. It's just way too easy to get slow-growing, late maturing genes in your flock.