Right now im on the 3rd Boil, I think after this boil is done and I rinse them off and change the water again. This 4th boil might be the last, well hopefully it is and they are clean enough. You absolutely dont want anything else but the shells left..
Once the boiling process is done, im going to either clean the grill and put them on it until golden brown, or into the oven. You dont want to over char them, you just want them lightly golden, even the egg shells so make sure to watch them. Unless your not just going for calcium.