Well, it CAN be tricky when introducing young ones to the flock. Thats another reason I like having the hen do it, because they are in the flock from the beginning.
I think free ranging also helps, or at least, have LOTS of space for them to get away if someone is picking on them. Introducing a butt-load of chicks all at once will also help, since no one should be getting picked on too much, there are just so many. Honestly, I have found that young hens are really the worst about picking on newcomers, roosters, (in my experience), are the protectors of the flock, and dont tend to pick on young ones.