[nelly]

If you're going to "wet" paint the frame, than blasting will probably leave too rough a surface to get a smooth finish.
Shot, especially steel shot, won't bounce off the old powder. It'll clean it off no problems.
It's the wet coat you're going to use that's dictating a non abrasive stripping.
Have a look around locally for a chemical stripping company. There's too many nooks for the blow torch and scraper method. It'll take forever and you'll not get it perfect.