I haven't tried soda blasting, but from what I undertsand it's not the right tool for removing rust.
The soda just isn't abrasive enough.
They work well for removing paint, and especially well on sheet metal that you don't want to warp with a sandblaster.
And they don't get sand everywhere.
However, a sandblaster can be used with softer media to avoid the warping problems.
There are some good videos on youtube.