Hopefully, someone can answer your "apply to" part. I've had great success with curing toenail fungus by just following the Miracle-Mineral-Supplement protocol. As I've said before, fungus stopped growing. It was removed just by the toenail growing and being clipped as part of my weekly clipping maintenance. It has not returned. I understand that you might not want to have your mother try the internal protocol. It works for fungus of the skin as well (ie. jock itch).
I remember that Jim Humble said to activate and add the 1/2 cup distilled water, then apply the Miracle-Mineral-Supplement to jock itch with your finger. That would be runny for the toenail; but if you have patience, you could try that. The main thing with the external use, is that you need to use the activated Miracle-Mineral-Supplement rather soon.
Humble also said that skin cancer has been cured with the internal use of MMS. It just dries up and falls off.