Thanks for the tips. The wire wheel does help get more of it off, that the sanding wouldn't touch. I will try the naval jelly next. Only thing I can think of is that some of the salts from the blasting or whatever caused this. However, its almost like a stain, or like a dye in cloth, as its not raised or anything.
Regarding dustless blasting, after the experience, I would favor traditional blasting over dustless as there is less issues with contamination from the water blasting residue. Also much more work to clean it up inside the car. However, it does have the advantage of limiting dust which can be important in a more residential setting. From my understanding, they do not add baking soda, but a product called hold-tite, which is a wetting agent that allows the water to flow off and not linger causing rust. Now, I had my car done in 40 degree weather, so the water lingered longer than on a summer day which is probably part of the problem. Anyway, I will be glad to share any other info on the process from my experience.
Thanks,
Chris