The Wheel-A-Brator I mentioned does exactly that - picture a rotisserie inside a cage with shot being thrown as the part rotates.

Never had issue with blast media left in the engine - rifle brush the oil passages, run water through the coolant passages.

I always knock out the core plugs and remove the gallery plugs before getting a block blasted.

The machines I have used did nothing that required getting the block machined again, just honing the bores. I think it relates to the media being used.
I have seen some blocks with mild peening of machined surfaces.