TRAINING
break someone in
to train someone to do a job; to supervise a new person learning a new job.It takes time to break a new worker in.Are they hard to break in?I have to break in a new worker.
cut one's eyeteeth on something
to have done something since one was very young; to have much experience at something. (Folksy.)Do I know about cars? I cut my eyeteeth on cars.I cut my eyeteeth on Bach. I can whistle everything he wrote.