A few things.

If you use soda blasting and don't treat the surface before painting, there will be adhesion problems. I don't use soda so I can't speak to what the post blast treatment process is.

Rough grit is fast but leaves the surface rough.

Coal cinder ( trade name Black Beauty ) can be had in various grits and is till pretty aggressive. Crushed glass works pretty well but be sure to change it as it continues to break down into powder.

Have a look on the TIP tools ( Ohio ) web site, they have bought up some of the older blasting companies and have good pricing on tools. Shipping grit gets $ so try to buy local.