For dietary things, I just keep my fats high and insulin low outside of my workouts. Make sure I'm not deficient in Zinc.
For supplementation, just wash my face and use Benzoyl Peroxide.
Other tricks involve actually washing my pillow covers, rather than rubbing my face in a cesspool of my own sweat and dead skin cells.
That's all for oily skin though, I've never been afflicted with dry skin. (So, OP, I cannot help with your question about your mom's feet)
As for calluses, pummus stone.