I toss back all eggshells from the eggs that I take (minus the few that I give away to neighbors) and things seem to be going good. As for the cook/uncooked, dried/normal, I kinda do a combo of it all depends on how the egg was used. Hardboiled eggs naturally have a cooked shell, but if I am pan frying the egg, the egg shell doesn't get cooked. Either way, I crush them up enough so the hens can easily eat them and that they no longer look like eggs. And, of note, this in addition to their layer feed, which has a decent amount of calcium in it. I don't typically add oyster shells unless I happen to have a mixed flock of laying and non-laying pullets - this case will get flockraiser with a side of oyster shells. Or just flockraiser if nobody is laying.