It's been a while since I made the first post, but thought I'd add a follow-up note for anyone else that might be interested. I didn't know this type of product was so readily available so maybe someone else will find this helpful.
I found this in the automotive section at Stuff-mart. It was fairly inexpensive so I thought I'd go ahead and give it a try. They had other brands so I don't know how it compared to others, but I was very satisfied. I just used a wire brush to get rid of the loose stuff, like Plain O TX said, then applied it with a disposable chip brush. You don't have to worry about brush marks or anything like that, but you wouldn't want to leave large runs big globs of it accumulating. It really does convert the rust into a black surface that is ready for painting or can be just left like that.
Instructions recommended a second application if it was going to be left unfinished. It would have looked ok, but I decided on a little black spray paint to finish it off a little better. (I was going to paint it black anyway)
Ended up being a much easier task than I expected. :thumbup: