I have had chickens for almost eight years now, and this is what I have learned so far. Some chickens are just not nice. I have been focusing more and more on friendly, people oriented, mellow breeds. I want to be able to relax around my chickens and even give a cuddles or a few pets. I have only breeds that have no problem with me reaching under them while sitting in the nest box now. I have a Green Queen that used to peck my legs hard. I started picking her up every time she did it and pet her for a bit (under the chin, on the cheeks, on her chest - I make sure to avoid the top of the head and back, and focus on places another chicken wouldn’t peck, so there’s no confusion), and put her back down. Turns out she liked it and after a few times she started pecking me and waiting expectantly. When she pecked hard I yelped and she learned to peck gently to ask to be picked up. She runs to me as fast as her little legs will take her. She has become my snuggle bug.
My newest roo (7 months old now) started biting my hands at around 5 months old, when I reached down for their food bowl or anything. So I started picking him up and talking to him and petting him gently each time he bit me. It took a few months, but now he just lets me pick him up. He is no longer scared of my hands. He stands between my legs to eat from the trough because we’re friends now and he knows I will keep the older hens from bothering him. My goal is to behave as un-chicken like as possible, so they can stop worrying about where I might be in the pecking order. Not responding to an affront by fighting or running, but calmly picking a chicken up and being gentle and sweet is not in their vocabulary, so it seems to jolt them out of their instincts and trigger the little bit of learning they are capable of. And I am sure there are chickens that just can’t adjust, too, but this has been working in my case. So, I recommend not imitating a chicken or predator in response to a chicken attack, but staying the friendly caretaker. Gloves and heavy pants help.