i personally don't have a bunch of chicks to keep track of but, i have a couple of the same breed i marked them by using a q-tip with a little food coloring and wiped it on their backs. It doez not last that long but, it works till they are big enough to put leg bans on.
That's a great idea! But my chicks are black I'll have to try that in the future. I may try the nail polish until they get big enough for zip ties. I just need to keep 3 of the OEs straight from the BCM chicks.
Blue Kote every 3-5 days on the tops of their heads. Since you are only sorting into two groups, it won't be as tough as marking each chick with a number or pattern.
Or you could put a hole in the chick's webbing for those 3 chicks. You can do it the same way they pierce ears if you have a helper. A small diameter nail with large head, a small scrap of wood, hold the chick's foot stretched out to reveal the webbing and hit the nail BARELY through the webbing then pull the nail out of the scrap wood. It sounds horrible but it is the exact same as the toe puncher.
If you like toe punching then they sell toe punches that look like finger nail clippers.