Yes if the snake strikes or does something not wanted, you should not reward them with being put back in the cage as that will reinforce that behavior. Taming them down will come with time. Its not something you can rush or force on them. Snakes aren't like dogs where you can more or less 'break" them. You will just make them stress more and more and get worse and worse. Since your boa is so new, I personally would just leave them alone and just let them watch the area, see you changing water every other day, spot cleaning any poops or pees, feeding them, just doing the daily stuff. Soon they will realize you aren't going to eat them and then them being curious will usually come over to see whats going on. Then you can start working with handling them for a little while at a time. I wouldn't do it daily until your boas are comfortable being out.
I started out with mine just handling them every couple days. You don't need to handle your boa all the time for them to stay mellow. A couple times a week is plenty and some boas like it more than others. Like Vicky doesn't mind coming out but she isn't nearly as gung ho about it as Rosey is. Rosey LOVES to come out and sit on me or ride around on me while I do stuff but she does have days where I open the cage and she just looks outside at me and turns around and goes back in the cage. After you have them long enough, you learn to read them more or less.
I never did the t-shirt thing. They learn soon enough from smelling you/the environment every day and seeing you doing the daily stuff in their cages. My advice is just let them settle in and get relaxed. First and foremost, you want to get them eating and pooping regularly, then you can start working with them.
Lol wait until you get that one snake that is a bear to work with. My JCP was a TERROR. She bit me at least 20 times and ive only had her just over 3 months. I've gotten her where I can take her out fairly confidently and not get bit but I don't let anyone near her as she will take a shot at anything within reach if it pisses her off haha. She took a shot at a pop can when I took a drink with her sitting around my neck/shoulders. She then hissed loudly at the can haha. Once you can tame down something like that, everything else is childs play hahaha.
Heres a picture of her. I call her Angry Allie lol.
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