I have three Silkies, which I tried feather sexing at a day old. I know it's not always accurate but figured what the heck. Anyway, I thought maybe one cockerel, two pullets, but as they started to grow realized I couldnt really tell them apart. He is too little for a leg band. I read on here to mark them with Sharpies, so tried that. But I hate those, they stink and I was only willing to do the outer tips of his feathers in one spt and it would wear off quickly. Then he got pooped on and I had to give him a bath anyway, so I dyed him with beet juice. Not all over, just his back and wings where he was dirty. I only did it pretty lightly too, but it has been a week and I can still see it. Though he is way slower to feather still than the other two and smaller, so I'm starting to be able to pick him out without the mark. The problem with dying chicks with most dyes though is that generally they are supposed to set for 15+ minutes and then be washed off, and chicks chill so easily. That's why ours was so light, I was so worried about the little guy getting cold.
