Learning is action. When a student doesn't understand something they have two choices, find help or keep being confused. I know the feeling of not wanting to ask a question, especially in a large group. The more experience we have, the more we know that we certainly are capable of understanding, it's finding that explanation that will "click" with us and the light will then come on.
How can learning be best effectuated by a teacher/trainer?
A teacher needs to use a variety of techniques to help students learn. Students will have different goal orientations and different comfort levels of participation and engagement. A teacher's job is to attempt to motivate each student. Some students like games and competition, others do not. While there are reasons to avoid help seeking, there are some students that do ask questions. I guess my point is, you have to deal with all kinds of personalities, comfort levels, backgrounds and goal orientations. Teachers need to make it comfortable for all types of student to seek help. Above all, the teacher needs to be accessible. Some students will be more comfortable one on one and others just need an avenue to seek help without conflicting with their own goal orientation.