You could strip your truck using any of the methods you describe.
A bigger compressor will be better in any application.
Siphon is usually less efficient than pressure.
Sift all your media through a screen and you will not have clogging problems (I have not had a single clog since I started screening silica/sand/used media). If you use graded media (more expensive) you will not have clogs, until you re-use the media.
Soda works fine and it will not warp metal. Soda media is a one-time use (much more expensive) but it is safer for thinner sheet metal and safer for you (safer environmentally, if you are blasting in the open). Soda is not good for removing rust. And, not matter what you have seen about painting over soda blasting, the best paint shops often use soda blasting, but they also use use soda-specific clean-up procedures (usually a neutralizing rinse).
No matter what type of media that you use, you will have to take care to get the media cleared out from crevices and pockets.
