Thanks so much for asking, the new chicks are doing great, I picked them up yesterday. 26 of them, the breeder gave us a few extra. They hatched on Wednesday like our four other chicks did. We have a total of 30 chicks now!!! So many little peeping sounds.
Here they are on the way home. They're Icelandic chickens so they don't have a standard color like most breeds. It's pretty much chance what comb style, head feathering, color, and feather pattern they are since they're a mix of the four Icelandic lines. Very interested to see what they will look like when they're bigger.
Some close ups of the different colors. I managed to get some of them to sit still on my knee for picture time. They're just so darn cute!!!
I gave 6 of these new ones to the mama hen (Ash is her name) who hatched her own 4, so she has 10 out of the 30 total chicks now. She didn't seem to notice the extras, clearly she's bad at math.

The chicks immediately understood that she was mama, which surprised me. Obviously they have good instincts, and it might've helped that the breeder was using
brinsea ecoglows so they understood they needed to go under something to get warmth.
As for the 4 broody hens, 2 of them decided to more or less quit which is good. They go up onto the roosts at night but sit on the nests for a part of the day acting broody. The 2 committed broody hens (Nutmeg and Cloud) are each set up with a dog crate in the coop like I did before, but they have not received chicks yet. I decided not to try it last night because I wanted to make sure they were still committed broody hens and not just copycat copouts like the other two.
I'm going to give just 2 or 3 chicks each to them tonight using the method y'all described. Probably not a necessary precaution, but I'm taking the cautious route because I really REALLY don't want to wake up to 20 dead chicks if the hens decide to reject them. That would be horrible, and they'd freeze to death with these unreasonably cold nights. Mother Nature didn't get the memo that it's supposed to be spring and not winter, we got snow yesterday.
So, if in the morning Nutmeg and Cloud have not rejected the chicks and they're all doing fine, then I'll hand the remaining chicks over. That way each of the three mother hens will have 10 chicks. Based on Ash's behavior, they don't seem to care at all if they're given extras once they're over the initial shock of "BLAH THERE'S A CREATURE UNDERNEATH ME." I guess we'll see.
I'll keep you updated!
And I'm so happy my broody set up was able to help you!!! It was literally just something I improvised with spare stuff I found in the barn since I didn't have the time or energy to build something permanent.

But hey, it works.