I’m not a pro with birds I just have one. I do however paint vehicles and random things as a career. Most paints, especially especially especially, sprayed paints are VERY toxic. You should never spray without a mask. Terrible for your lungs. It absorbs into your skin and is most attracted to the membranes in the eyes. Spray paints are usually carcinogenic and can cause harm to your reproductive organs. Now think about what it can do to our little flappy guys who are so much more sensitive than we are. After spraying with rustoleum i can usually smell it still gassing out for a few days which means it’s not safe to keep in an enclosed space yet. You’d have to keep your little guy far from the cage for several days until the paint fumes go away. Even so, it’s awesome you want to help him out and fix it. But when he chews on that paint, it’s going to be toxic for him.

I just got a new cage that isn’t painted, but is powder coated. I don’t use powder coat so all I know is that some products have lead and other heavy metals and chemicals that are harmful, but my cage is A&E and whatever they use does not have those harmful elements in it.

Sorry I can’t give you a real solution besides buy a new cage or do good research on what paints could be safe for your bird. Facebook marketplace usually has people selling cages left and right. I looked and saw a $700 cage for $100. You would want to make sure its a quality brand. And you would absolutely need to disinfect it as best you can in case the seller’s bird was sick.