Soda blasting? That's a ubiquitous process being performed literally all the time.

Yeah, blasting, grinding, cutting, forging, and dozens of other industrial processes are nasty and messy, but that isn't the hassle. The problem here is secrecy and finding shops with a large enough blasting bay (there are thousands of auto body shops with bays for blasting full size trucks and other large vehicles - literally 15 on Google Maps within half an hour of me) and having laborers with top-secret clearance to do the work. All so 1970s tech can stay a secret.