Training a brand new "cadet" with 250 hours is a different task to training a hairy old 55 year old captain. The trainer needs to understand where the trainee has come from and adapt according to the trainees background experience and personality. One size does not fit all.
A good training captain, or indeed, a training FO needs to be adaptable amongst a host of other skills. Each trainee will learn differently. the trainer needs to adapt and understand to the trainees needs. In the olden days, trainers had just one way of teaching. Normally "monkey see, monkey do." If that did not work, then .. clearly the student was not good enough. Now a good trainer tries to understand how the student is learning, and adapts to that. For instance I tend to learn visually. Others need numbers and routines. Others are a mixture. Everyone is different.
So a brand new 20 hour cadet will need instruction. You talk, he listens. As the cadet begins to improve the instruction reduces, and you need to support him, and encourage him in improving his skills. More coaching than instruction. Towards the end of his training course the Cadet, should be able to get on and do is job with little or no input from the trainer.
With a grumpy old Captain on a conversion course it is a different matter. You show him the type specific stuff, how the seat moves, where to keep his glasses and pen. The best place to put the coffee cup. Impart a few words of wisdom about the new type. He does his thing and you mostly are mute in the right hand seat.
Bad trainers: Talk too much. Wave their ego in your face. Are inconsistent. Inflexible. Rigid. Never listen. Can't teach.
Too often trainers are doing the job for the money, and status, and not because they want to teach and impart wisdom and knowledge.
There is nothing more rewarding than watching a check ride in the simulator, watching a mediocre performance begin to unfold, and then with small input, settle the situation and tease out of the crew a good check ride. They learn something, and I always get to learn something. A bad trainer loves to unsettle a crew, and secretly delights in a bad performance. His ego gets fluffed up, and the trainee has his confidence rattled, and goes away learning nothing other than the training captain is an @rse.
All IMHO.