Not trying to play the devil's advocate here
, well maybe I am, but whatever.
Water + Bare Steel = Rust
I know its not going to pit in the hour it might take you to go from prep to etch or epoxy, but it will form an oxide very quickly. Correct?? And then you're back to the same place you were a day ago when you started blasting. I don't really know what the answer might be.
Plastic media?? Buy a drum, build a booth out of plastic shovel it up off the floor and strain and repeat?? Any ideas