I think you are not getting responses because it's hard to imagine spray painting solid brass. The cheap imitations, yes, spray away. But if I were you, I would put the lamps aside, go to Goodwill, and for a few dollars get a couple cheap lamps and spray them black.

But to answer your question, clean the lamps of any dirt and grime, tape off anything you don't want the paint to land on, and then apply the spray paint.

You're probably right. I'll just put them away and get something else. Thanks.