Selecting Eggs for Incubation: Flock Expansion

So I'd like to get some tips or guidelines that chicken raisers use to select eggs for incubation.

I've got 9 Easter eggers, 5 Rhode Island Reds and 2 barred rocks (one is actually solid Black). The Rooster is a rather large, good tempered EE. He's protective, stands his ground and is very vocal. I've had a couple mini-battles with him but for the most part we're on good terms.

I'm trying to build a flock primarily for eggs and to clear/fertilize some scrubby pasture.

I'd like to end up with about 100 birds for the task of land clearing of which 50% (males) will be sent to "freezer camp" at the appropriate time. Assuming that will leave me with about 50ish birds to select through for egg production, meat breeders and culls.

So that's the goal.

What I need to know is:

Of the eggs I get for my current layers, which ones would be the best to save? Does egg size matter? Shell thickness? Shape?

How long can a fertile egg sit idle before it needs to be incubated? I'd like to get all of them done in once shot but with only a dozen eggs a day coming from the coop, I'd need to set them aside til I have enough to fill the incubator.

Any thoughts on good crosses?

I usually pick eggs that are clean so that I don't have to clean them and risk compromising the integrity of the shell. I also try to choose eggs that have good shape without blemishes, because many egg characteristics are heritable.

I've held chicken eggs for ten days before incubating, and the hatch rate was good. I don't use an incubator, though, I let hens do the job. you might consider that option, too, supposing that some of your hens go broody. if you want 100 chicks, you certainly couldn't let the hens hatch them all, but maybe keep an eye out for broodies and let them do the job for at least a few. I've found that chicks hatched and raised by hens are better foragers and keep a better eye out for avian predators than chicks hatched in an incubator and raised in a brooder. that the hens look after their chicks also helps their odds.

never intentionally tried hybrids. the few chance hybrids I have are clever and wily birds, but not particularly good layers. very good mothers, though. I believe they are bantam Cochin/Red Sex Link crosses, but I'm not entirely sure about that. the Sex Links are hybrids to begin with, so it isn't surprising that the offspring are a bit strange.