Ahh! Good idea! Yep, new territory! My brother cured a persistent infected ingrown toenail with a daily 1 hour swim in the community pool (over 40 years ago!) Absolutely do not give it internally as it requires quite a bit of water to wash down not practical with an animal.
I would suggest trying different strengths on your own feet. Soak them in a solution and see how they react. Go from there. If you have an open sore or something so much the better. Then you will know if there is sting involved.
But it still remains that they must get into a cleaner, dryer environment until they are completely healed or all will probably be for naught.
Again, if you have access to this ointment you speak of, try it with MMS on yourself to see how it feels and reacts. Or if you have no open wounds a willing volunteer is always nice!
You really don't want to be ouching a large animal any more than you have to, especially if you are bent over by their feet!