+1 for the 0000 steal wool. It's worked for me well in the past. I've also been able to remove light surface rust before spraying it with PB Blast or WD-40, letting it soak a few mins, then wiping it off.
If the rust pitted the surface then it's a little more work. If you want to remove the pitting it'll require polishing, sanding, or draw filing depending on how bad it is.
If you search the web you can find information on using a molasses and water mixture to remove rust. Evidently very common in the auto restoration business where large parts need to be derusted. Supposedly leaves paint and one reference referred to it leaving the remaining parkerized finish intact. I know several people who swear by the process. I don't know how it would affect blueing.