Hi David,
As far as I know, the nystatin is an anti-fungal drug. Unless you have thrush or some other sort of fungal infection, I'm not sure why it is part of the mix.
When I was using the magic mix (called the Pink Lady by my doc), the recommendation was to swish and spit or swich and swallow, whichever seemed to work best. I found it too thick to swallow so mostly spit. I never noticed the benadryl making me sleepy, I had enough narcotics to accomplish that.
As the radiation continued, I found that I had to alternate between the magic mouthwash and a simple rinse of baking soda (1 tsp), salt (1/2 tsp) and water (8 oz.). It was helpful to me to alternate between the two. Good luck with the rest of your treatments. - Sheldon