The ones with the biggest, brightest combs & wattles are probably males.
You may be getting close to the point when pullets start getting big red combs too, but even a mature hen has a smaller comb than a male of the same age & breed.
Have you heard any of them crowing? If so, the crowers are males. That's a way to check some of them.
If you're going to process them, I suggest you do them one by one, working from the biggest comb on down the line, and check each bird for testicles (white bean-shaped things up inside the center of the back, against the spine). Each time you find testicles, you know that one was male.
If you find one with no testicles, but a cluster of egg yolks forming in that area, you know it was a pullet. If you started with the big-comb birds and worked your way down, at that point you can be pretty sure that all the rest are females. I've done this when I was unsure of my sexing on some chickens: it reassures me about each male I correctly identified, and if I am wrong on one it makes me stop before I kill any other females.
For the picture in that post, I think the one in the back right with big comb & wattles is male. I think all the other heads in the photo are probably female. Or else some are males that are being very slow in their development (possible but not too