In my experience, RIRs have been the most friendly and outgoing of all the different breeds I've raised over the years. That means that once you have a break through, you're gonna have some fun chickens.
Here's what I do with my chicks. I sit and hang my hand in the brooder, and just talk softly to them, even make little cooing and clicking sounds like a mama hen. In a higher pitched, quiet voice I say things like, "Hi, my babies! I wish you'd come say hi to me." I just say nonsense things, getting them used to my voice.
Having a yummy treat works wonders as well. I hold worms for them. I don't let go until the worm is jerked from my fingers. Fresh fruit, popcorn (unsalted), corn tortillas, even some BSFL (mine don't like those until they are older), just yummy treats for them to associate with you.
Something else that I do, which some on here may not like, is that I will pick up the chick and hold it in my hands. One under the breast bone, with the legs between my fingers, and the other hand on the wings, gently keeping them from flapping. Then my top hand shifts so the side of my hand is holding the wings down while my fingers are making a "blinder" on the side of the chicks head (not touching the head or neck), blocking their sight on one side while I put them close-ish to my face. I turn my face sideways and look at them with the one eye, like a chicken would do. I then speak softly to them, as they focus on me. I move my head like they do, without breaking eye contact.
I do this daily with my chicks. Most of them will just hop on my hand when I put it into the brooder.
I do the same thing to my grown chickens, when we have to catch them on occasion. That can be a scary situation for them, if they don't feel like being caught. It calms them almost immediately. Even strange birds I've never handled before, it works like a charm. It's like you are speaking their language. You make them focus on you while you let them know you are safety.
When I'm outside with my birds during free range time, if they see something that scares them, they run to me. I'm allowed to flap and make noise, and not one of them runs away from me. I have 31 grown birds. Every one of them turns back into a chick with me. I swear by this trick.
My husband is doing this trick with a cockrell that is NOT fond of people. This little guy has to adjust his behavior if he wants to stay here. We don't keep naughty roos. It seems to be working, and they are developing respect, if not a bond.
Try this trick! Let me know how it works. Do it several times a day, and I bet your chicks will be a lot different. Oh! And call them by their names as you look at them and interact with them. They are smart. They will learn who is their safety.
