As a person who teaches memoir, people often think (wish?) I had a higher degree in English, Literature or Creative Writing. I have had many feelings of inadequacy about my Bachelors in Anthropology and French. But mostly, I have found that my students trust me more based on my energy and the way I hold the space for them rather than on my "qualifications", especially since the focus in my classes is less on writing as product and more as process.
Lately, in the last year or so, I've been stretching my wings more and more in helping students with latter stages of the process, working towards creating product. I've had to plow through much fear about inadequacy and how much can I charge for something I am just starting to do now, etc, etc.
But what I find in going further with students' writing - editing, critiquing, guiding larger projects towards finishing - is that I learn as I go along and so do they. Even better, we teach each other.