Soda blasting would be a feasible option to remove the surface rust on panels without fear of warping them. I have witnessed the process and it did a very good job on light rust. The deeper and heavier rust had to be worked out with more agressive media but the surface was left in a great condition for further treatment.

The soda blasting can be done wet or dry. In this case it was done "wet" with a very small amount of water included in the blast stream. I was told this neutralizes the rust and prevents flash rusting of the blasted panel. Futher treatment of the bare metal with a phosphate solution was recommended for neutralization of the sodium-bicarb residue on the metal. After which an epoxy primer could be applied.

Chemical dipping is also another means of getting rid of the rust and would get to the back side of those cowl panels and door pillars that cannot be reached otherwise.

There are vendors with trailer mounted soda blasting rigs that can come to you to clean your metal. Check around in your area. I would suggest calling some marinas to see if they have someone who does this as the process is used to clean boat bottoms.