I’m so sorry that you rooster was injured and is struggling now. If you can keep it from getting infected, it may be able to granulate in, even though it is a large wound. I myself wouldn’t try to debride any dead skin at this point but you may need to gently loosen dead tissue from the wound itself if you see loose material when you flush. Did I see that you are flushing with warm saline or dilute chlorhexadine? Keeping it clean and covered seems like a good plan. Praying for health!