Have you done your bird bath yet? If not I have a few suggestions. I have been working with cement, making garden art, and I there are a couple of ways to revive an old bird bath. You can fix any cracks with morter mix. As far as painting goes you can use cement paint, or cement stain. If it has already been painted you don't have much choice than repainting it unless you strip it which is a nasty job. Or you could add another finish layer, say morter some tile, or stones on it.
Dee