Soda blasting is done w/ a special rig that sprays it wet. Not something you can do yourself.
NEVER sand blast sheet metal. You can do small spots, for rust, but if you try to blast a panel it will be warped to death. Even doing small spots will distort the metal in that area.
To strip paint use a plastic media. I have priced having a car done for a customer, for a mid size car all over it was about $400.00. (That is a Florida price BTW.)