This is just my take on it. Others probably do it another way, because i'm odd. Cooperative association is something I use in retraining abused animals and the wild or semi-feral, so it's what I do with my chickens.
I encourage a lack of fear of hands by providing treats from my hands only. Allowing perching is part of trust building. if i do have to pick up a chick and I do so at least once daily - I don't release it until it has relaxed.
The animal that gets the reward of evasion or escape by making a ruckus will repeat it for that reward. It requires patience and timing. Be aware of what you reward, fuss or relaxation.
Work on treats for perching time, require relaxation before release. Hanging on for the sake of affection when the animal's instincts have kicked in only increases the instinct.
Encouraging association, perching, and trust will increase the time the animal WANTS to associate with you and will willingly do so.
Some animals, and some - both individual birds within breeds, and some breeds more often than not, do not want to be cuddled by humans. Cuddle requires a combination of trust AND a preference for the pressure and physical contact of handling. if the bird has been born without a tolerance for physical pressure and handling, all the work in the world is more likely than not only going to help marginally.
you can only fight gene-based tolerance of sensation or stress so much. After that genes win.
Allowing perching, increasing time and the value 'or goodness' of treats, will work with some and not with others. The best treats for the longest calmest contact. Don't surprise them if you can help it.
When you ARE offering contact, make a noise or say something, each time before you move your hands. No, they don't know what you are saying but they will LEARN to ASSOCIATE sound with action. I offer food, I say 'chick chick', I offer my hands I say "come here". I'm done. I say all done. I put them down, I say, down now.
Animals LIKE predictability and habit, including sound cues. Simple animals like chickens won't often make the training leaps that many animals begin to. But they will learn what happens after a specific sound. Predictability creates trust.
If they're Freakers by birth, there's not a lot you can do. If they're just growing up, then you've got a chance at it.
The more patient you are, the better your chances.
The wildest of animals can be taught to 'hang' with humans if there is the right pairing of reward and trust.
