To start with, when I use an egg, I wash out the inside really well just using water and my finger to get the slime out. Then I set them on the back of my sink to dry. When they are dry I toss them in a coffee can on the back of the stove. When the can gets full, I bake them. I bake them at 350 for about 10 minutes or so. then crush them up. I put some in butter bowl and use a potato masher to break them in really small pieces. I keep adding shells and smashing/grinding at them until I get them all done and they are small enough that the chickens can grab a mouth full without having to break them up themselves at all (basically the size of the oyster shell you can get to feed them). Mine wouldn't eat the oyster shell (well about 2-4 of them would out of about 36 hens) so this works better. I have had several flocks over the years and the only time any of mine eats eggs is if I accidentally drop one when I am collecting eggs LOL. I did have an egg sucking cat though hehe.