Considering that the most powerful tool every therapist has in their work are themselves then the best training they can get is to have enough therapy themselves before starting to see other people. This also gives the first had experience with transference-countertransference.

This is the model practiced in psychoanalysis - the personal analysis is by far the most important part of the training. Sure, the training also includes theoretical work and case work under supervision, but this can only start after the personal analysis is already long under way.