Coppertox is not very exspensive and readily available at most farm stores. It works very quickly. You really need to get on it as it can get very nasty and cause a lot of damage. Also until its better the horse should be kept in a dry place with hooves picked daily.
usually either tamed iodine (4%) or clorox full strength once a day and keeping the feet dry and clean for a month or so will do the trick just fine. If you don't see improvement after the first couple of days, check with your vet, maybe it is a hard to kill variety needing special treatment. I have also heard of people using turpentine, and formaldehyde... but have not tried those myself. good luck
The bacteria that cause Thrush is anaerobic (survives best w/o oxygen) and they have no real reason to surface (where a topically applied product would kill them right away). Sugar, on the other hand represents a food type medium for them, so they more or less come out to eat, and the betadine kills them.