After over a year of trying everything under the sun to battle my geldings thrush I finally won using "Pete's Goo", which is a 50/50 mix of neosporin (I actually used a generic brand) and athelete's foot cream. Three times a week I picked his foot thoroughly, sprayed his foot with hydrogen peroxcide to clean it, then used a syringe to get the medicine down into his heel crack and fill it up, and I may have gone a bit overboard but it worked best for me, but I also put some all over his frog area, central sulcus, heel, and in the back of each collateral groove (he actually had a hole that went from one of this grooves underneath into the frog, as soon as I figured that out healing sped up as well), and then I covered the whole bottom of his hoof and up onto the heel bulbs concentrating the most over the heel crack and frog with a generic A & D diaper rash ointment to create a barrier to protect from urine and wetness. Which I also kept him out of the mud as much as possible and kept his stall as clean and dry as I could with going out there 3 times a week.
I know most of the things you'll read say you only need a little bit, or like a pea sized amount and I tried that for awhile first but wasn't getting much of a result, so as a last ditch effort (was seriously losing hope of ever getting it healed up) I decided to up the amounts and cover my bases. Worked like a charm. Like I said, after over a year of having little to no results, it finally all healed up after a few months of doing this. And a few months probably sounds pretty long, but his frog was pretty deteriorated and the crack was deep, not to mention a lot of other products I tried seemed to dry his hoof and damage it which made it worse overall in my opinion. So it cost me around $10 each time I bought the neosporin, athlete's foot cream, and diaper rash ointment and each batch would last me a good few weeks. As maintence since it healed (it's only been about a month), since I'm scared to go cold turkey with the medicine, I've kept applying the diaper rash ointment to protect it, as well as spraying all of his feet with apple cider vinegar as a preventative. Hope this helps!