I tried adding it to wet crumbles but she wouldn't eat it! I think that fruity smell isn't attractive to them, I broke it into pieces, and then opened her beak and dropped in a piece at a time... She is a pretty good natured hen so it wasn't all that difficult!
My hens don't like the oyster shell. I have everyone in the house rinsing their egg shells and dropping them into a container on the counter. I crush them a couple of times a week by just crumbling them in my hands until the pieces are about 1/4" at the most. They absolutely love the crushed egg shells. They vanish almost overnight. The reason that you need to make the pieces small is that you don't want them to know that they are eating an egg shell because they might begin eating their eggs.
I am going to try to find liquid calcium. I'll let you know the info when I find it.
I use a Magic Bullet to grind the egg shells to a powder. I used to just smoosh them inside a baggie with a smooth rock but discovered the blender method was faster and smoother eggshell pieces. I heat the eggshells in the oven for 10 to 15 minutes to get rid of any possible bacteria and collect the toasted eggshells to use in one blender-full. The powdery eggshell in the blender is good to add to the raised garden bed soil too.