I own a soda blasting business of 5 years and joined the board today to post comments and answers from my experience.
Soda blasting can only be done with soda blasting equipment for true performance. Sure, you can stick baking soda into a sand blaster or plastic media blaster but, to complete a full car body would be very expensive. Baking soda is a one pass media that cannot be re-used like sand or plastic media. If you cannot control the flow, the excessive waste will empty your pockets buying the media.
Baking soda does remove bondo but, will not remove rust.
It also must be rinsed thoroughly with water, yes I did say (water) in order to remove the soda completely from what you blasted. After rinsing you want to towel dry all areas to prevent thick baking soda residue runs. These runs can also be removed with a combination of vinegar and warm water if it has air dried.
After this process is done, soda leaves a invisible layer that acts as a buffer to the metal. If stored in a dry area with no moisture or humidity, the metal can go as long as 6 months before flash rust appears. That means no immediate need for primer.
Etching primer is a no no, only use epoxy primer to the bare metal first. All areas must be cleaned with wax & grease remover before primer as normal.
I have never had an unhappy customer or any problems with paint coming off the car.
To comment on the rusted areas, soda removes all surface rust down to the substrate. It will leave the areas a dark black color. What works best for me is a hand-held sandblasting gun filled with #5 sugar sand. Go over all black areas until the metal turns white. These areas also have to be primed immediately.
No need to remove or protect glass or chrome from the car either, baking soda is non abrasive and does not generate heat.
I hope this info has been some help to many concerns about this process.