Know your mouth! How does the following assertion fit, if at all, with your experience as a teacher of pronunciation?
Your impact as a pronunciation teacher is directly proportional to your understanding of how you make sounds in your own mouth. Not your theoretical understanding, but your physically experienced understanding, your ability to sense in real time the movements of the different muscles of articulation as you speak, and how that relates to the phonemes you produce
If you know what is going on at the physical level you have a real chance of being able to transmit that to your learners. If you do not know what is going on at the physical level, and your mouth is something of a mysterious black box, then you are reduced to varieties of pronunciation teaching known as repeat after me and no that’s not quite right, which are fine as part of a toolkit, but not as the dominant or default part.