I found making my own breeders from my own litters and handling them alot as babies makes the best breeders.
All of my adult female breeders I raised from pinkies and not one of them will bite me even pulling babies while they are attached to momma getting milk.
Trying to tame adult rats is tricky and takes time building trust, and lots of treats
Yogurt, mashed potatos, banana are all treats you can hold and control.
Yogurt and mashed tatoes in a spoon and let them eat it out of the spoon, don't give it to them, you are in control, in a good way.
Soon they learn to trust you, some never do, but most come around if they haven't been abused as babies.