Well, I dont mean to toss a wrench in the machinery here, but how do you know if you have made all the repairs if you don't blast it first? Over years and years of use, people do repairs, etc and paint over it. If it was a competent job, you have NO idea whats under there until you blast it.
Another problem is the thickness of the metal where rust occurs. Blasting can expose very thin areas that need repair. To get a really good look at what needs repair, I don't know of another way. Dents and dings I understand, but when metal gets really thin, and you have a patch panel ready to put in, you may need more repair and not know it.
