When I was young our church choir had a "powerful instrument" too. I never thought of it from the choir director's point of view. Sister Alma is a fun accompanist.
These results are superb. There are definitely some tips for all conductors here with the encouragement of a reticent singer and the helping of the over-enthusiastic singer. Remember her key words here are "Listen to each other if you are going to be a group." I sense a theme here.
Now, here is the performance.