It's a paint brand, you can use a spray or can -I usually spray. There are other brands, but from reading a bit, that particular brand is one who has responded to a lot of bird people stating it's safe for birds as long as it's completely cured. Now I've never used it for my birds cage, however birds are so sensitive and if Rustoleum feels confindent it's safe for them it's probably pretty safe for our rats.
when I've used it, I have not used a primer. Use a brush to make sure there is no rust on the pan and it's clean and dry prior to painting. Each coat, I wait probably an hour or so depending on hot it is. You want it to cure for about a week or more before use.
I've used it for galvanized pans as well as cages that were previously powder coated and with age started to chip. I've used it for both rats and ferret cages I've had in the past. You will probably first see chipping from your homemade version in places where metal hits metal regularly. I've had cages/pans powder coated as well in the past. It will take longer before they start to chip, but they do chip as well.
Now my large bird cages, those are made with different metals and I have no idea on what method they use for the paint coatings, but usually the paint lasts for years. I'd love if small animal cages were done similarly.
