So my bauer 3000 cage is pretty rusty, had it about 5 years now. I sanded off most of the rust but I wasn't sure if it would be safe to paint, would it affect the shields integrity or anything. I was thinking some regular black rust-oleum would do the trick.
Don't think painting would harm the integrity of it...but maybe the rust has. If it has eaten through anything, ought to get a new cage. But if it's still smooth and everything looks ok you'll be ok but it wouldn't be certified anymore since you modded it.
But just make sure it's nice and clean, put some primer on it, and when painting, do light even coats.