If you're not in showing season, cut all the hair off<---fetlock hair trim the coronet hair back as if you were getting ready for show season, cut any excess hair off the fetlock joints.
The bacteria/fungus that creates thrush thrives in moist environments so, keeping the hair cut back in those areas helps reduce moisture and lets the air dry the legs out faster
You could make a 50-50 mix of generic diaper rash cream and some sort of people antibiotic ointment.
Diaper rash cream is full of zinc oxide which is a healing property and it stays on pretty good. It won't last all day (you will have to re-apply twice a day) but diaper rash cream stays on longer than anything else I've tried and it's fairly cheap
You don't have to make a perfect "50-50" mix either. Just squeeze them onto your finger tips, making sure the diaper rash cream ends up being the bigger amount.
Cutting all that hair back, also makes it easier to put the creams & ointments on
Hope this helps