Calstar,

I and a few other painters I know, use Star Blast by Dupont. Cant think of the size though. You could try emailing Toby at Hot Tubes or Chris and Brian at Circle A. A walk in cabinate with a fresh air pack and and a pot style blaster is the best setup for stripping. Cabinets are great for bare metal prep as all you need to do is give the frame/metal some tooth.

Slag, nothing takes it off. It has to be removed prior to blasting (soaking, scraping, etc). A thin burnt layer will come off but an actual glassy chunk, no way. That stuff is hard.

Paint, burn it or do something else prior to blasting. Stripping paint with a blaster sucks. For powder coat, send it out to be dipped/stripped first.

Hope this helps-Chris