@Susie the main reason I premix my micas in a bit of oil is I can more easily and quickly stir the colors into the batter without having to use the stick blender - especially when I'm trying to maximize working time. For a one color batch I would just add the dry mica.
I have very hard water. My skin is average, not oily or dry. I have gone to 0 superfat and I love the way my skin feels. I did use superfat in my first shampoo and shaving soaps but they are curing. No verdict yet!