When cattle are dehorned at a later stage they get the same thing. The vet always reassures us that it's fine, applies antibiotic spray and fly repellent, and isn't concerned about a bit of pus-y discharge for a few days so long as it's clearly healing.
But yes, we do them out of fly season. I'd be at it daily (or nearly) with the fly repellent, and probably try to cover the holes with fine gauze or something, if there were flies about.