-What are your preferences when incubating shipped eggs?
Here is what I am doing with mine - let set for 24 hours, then set them in the incubator. Don't turn the first 2 days.
-Which do you think would have a better hatch rate?
I have 2 hens currently broody and I set my shipped eggs in my incubator. I will put the chicks under the hens after hatching if hens are still broody at that time. Shipped eggs hatch better if incubated upright and not turned hte first two days, neither of which is possible under a hen. Plus I don't want to risk these eggs in case she decides to leave the nest.
-Should I separate momma if she sits on them?
I always do. Even with barnyard eggs. I make a separate nest out of a cardboard box, put fake eggs in it, and move it elsewhere in the coop. I put a makeshift pen so she can't go back to her other nest, and has food & water close by. If she stays in it a day or two, then I give her eggs to hatch.
-If so, when should I reintroduce her and the babies back to the flock?
I put broody and fosters together in a very small pen or large cardboard box until her "sit on nest" hormones stop and she is mothering the chicks adequately - leading them to feed & water, warming them up, etc. Then I leave them in a somewhat larger pen in the corner of the coop. When she is ready to introduce them to the flock, she will fly out of the pen. (My broody - like 2 weeks or so. I thought it was too young, but there was no keeping her in). At that point, I open up the pen a little so they all can get in & out easily.
-If we incubate and then sneak them under her after hatch, do I separate all of them from our flock?
See above. DO THIS WITH CAUTION, NOT ALL BROODIES WILL ACCEPT FOSTER CHICKS. SOME WILL KILL THE CHICKS.
-When we get the eggs, before incubation either way, what are the best steps to take to give them the best chance at survival? Candle? Sit for 24 hrs?
Candle very gently, let sit upright for 24 hours.
-Should I candle to check progress?
Days 7, 14, and 18 (lockdown)
-Also, I have 2 broody hens who refuse to sit on separate nests. If I leave everything as is, does it hurt to have them both share the nest and eggs?
I don't like to do this. I have had some terrible boodies, that poop in the nest box. Yucky eggs, don't hatch. 2 hens = double chance of this happening. Also, when I have 2 laying hens try to use the same nest box at the same time, I sometimes get broken eggs. I don't see why this wouldn't happen with broodies. Finally, sometimes 2 broodies will fight over the chicks, this can result in injuries to chicks and/or hens, or dead chicks. 2 broodies = 2 nest boxes and 2 pens (or at VERY least, nest boxes far enough apart and positioned so they can't see chicks that tumble out of the other nest.)