I media blasted my car but I took it apart first. If I wasn't taking it apart no way would I try and blast the bottom. It took weeks of compressed air and vacuums to get all the media out but you can get it out. I was amazed how much blast media was in my rockers.

I think you really need to decide what you want to do and when. I hate the endless screwing with stuff and if I'm going to put time in on something I only want to have to do it once and have it done right. That's the only reason I took the approach I did with my car.

 

The shell on a trailer down a bumpy road works well to knock it all out.

 

Thats what we used. Putty knife and different scrapers and old cruddy screwdrivers.