Around here BB is about 8-19 bucks a bag and is pretty aggressive. After using one bag I still have the other leaning against the wall.
I go to my concrete mixing company and but silica sand that is SIZED so it don't clog up stuff. I bought some not long ago and it was about 4 bucks for a 50lb bag. It comes in Fine, Extra Fine and Medium. I like the Fine which on the bag is described as 45 grit.....I think. I use it but never pay attention to the writing anymore!
It will depend on how bad your frame is. It could take a couple hundred pounds and I have done them that took much more.
For what its worth, I sold my pressure blaster and promised myself I'd never use one again. If it don't go in the bead blasting cabinet it goes to someone else. Think about it.
