I have used Equaide on ancient proud flesh and it worked. You can scratch the crispy tissue because it does not have nerves. If you can see pink tissue or a few hints of blood it shouldn’t bother the horse. I used it on many wounds because it helps with scabbing. It is easy to paint on and seems to help things heal more quickly. I clean it daily but don’t scrub it all out. I hold a damp gauze on and let it soak, then clean it up and apply more. Yes, it is expensive, but a little goes a long way.
Copper sulfate eats the flesh in a wound, but if you are sloppy around the edges it can also hurt healthy flesh.