So an assembled engine can be done no problem, without worrying about stuff getting in the engine?
As Zunspec already has replied, everything must be disassembled before blasting.
The process involves glass beads and every single one of them must be removed before assembly.
I get a few customers that drops off oily, greasy, and just plain dirty unwashed parts thinking that the blasting process will get rid of the dirt.
In essence they are correct, but the grease and dirt will contaminate the media and that in turn will give a worse end result and a higher cost due to more maintainence to the cabinet.
So, everything shall be disassembled and cleaned as well as possible before blasting.
My take on it is that I can do the disassembly and cleaning for the customer at a price, or they can do it themselves and come back later.
Most guys choose the latter...