How old is the toy? Is it a collectible?
It's probably too late now but if it's an antique you should of left the toy with it's original patina. A light coat of rust converter would have been the best option along with some gentle cleaning. The converter would have turned the soft red rust to a hard black oxide. Repainting an antique toy kills about half it's value. On the other hand if you'll be keeping it in the family then resale value is not an issue. I'm sure it'll look great after painting.
Would love to see overall pics!