I didn't know you had to wash or bake them. Not sure why that would be important. You do want to pulverize them good so the chickens don't know they are eggs. Maybe it is easier to do so after washing and baking. Crushed oyster shell is pretty cheap, which is why I never bothered to process egg shells.
I boil and bake mine because i store them in jars, and i don't want any kind of bacteria to develop while in storage. Baking also makes them brittle and easy to crush. It isn't necessary to pulverize them completely. You can just break them up so that it's in little pieces that they can pick up with their beaks. They don't associate the pieces with their eggs. I like to purchase as little as possible and make use of resources as much as i can, so i feed their shells back to them. So far, all of my girls are laying eggs with very hard shells, so i think it's doing the trick.
I toss mine in a bucket, wait for them to dry, crush, and throw in the coop. So long as you don't pile too many and prevent them from drying you don't have to bake but baking will dry them out faster instead of waiting a day or 2 and you don't have to worry how many egg shells you have. Otherwise the chickens aren't going to encounter anything on an unwashed air dried egg shell that they aren't exposed to daily in their yard and coop. I don't think leaving even chunks of egg shell will encourage egg eating. I just crush enough it's all flat chips so it doesn't take much effort. You can't always get oyster shell around here.