@Beer can - I don't really have any "secrets" for hatching so many roosters.
I just collect the eggs & incubate them. Often, I try to set ones that are similar shape/egg shell color, as to get the most from the same hen. (That's not possible for everyone, as some hens lay slightly different egg shape, size & color, others are almost identical each day.)
My theory is that for every egg 1 hen lays, it's a 50/50 ratio. But, if you incubate 40 eggs, all from the same day, all different hens - the ratio may be "off balance". Last year, I'd save up eggs for several days, then, compare them & I'd often find ones that were identical or very similar to each other. For example, one group had just one green egg layer, so that was easy. I'd set all of her eggs, and she threw quite a few pullets, less cockerels. Another hen, I only got roosters from her. I've read that it's the hen that determines whether her offspring is a hen or rooster, but again not totally sure if that's accurate or not.
Just observed & tried to do take notes on each hatch, keep good records of the chicks with the wing-bands, etc. I do know my first two hatches under broody hens back in 2012, I just put eggs under the hens that were laid in one day. The ratio for those hatches was 2 Roo to 1 Hen, and 5 R to 2 H. Yet, I just see it as an experiment & even though I'd like to tip the scales toward more pullets, if commercial hatcheries haven't figured out the "secret", I'm not so sure there is one.
As far as the roosters, I've never been able to tell who's who @ such a young age. Usually, I wait until they're 8 - 10 weeks old, but this time it seems to be very obvious.
Warning: PHOTO OVERLOAD!
Quite a few have head-spots, b/c of the barring gene,
and I'd say at least 95% of those with head-spots are roosters.
Some are already bright pink, and it was that
way before I picked them up.
This single comb is much smaller,
and pale yellow
Same chick - see how can't even see comb or wattles
from the side - most likely a pullet.
Even the pea/single comb crosses were pretty easy
Cockerel side view
It was also interesting the color difference
in the little cockerels vs the pullets
Very small single comb of a pullet
While sorting them out, I put all the cockerels & pullets in
a separate bin, so I'd make it easier to catch the last ones.
And here's the bin full of cockerels!
vs the "empty" bin of pullets :(
Warming back up under the hover brooder