Welcome aboard! Nice Toaster!
The problem with blasting is that some media can have the potential to create problems down the road if things aren't meticulously & thorough cleaned afterward - and this is with a disassembled engine. An an assembled engine I think there are just too many places where stuff can get in and lodge and create issues from accelerating oxidation, to plugging oil galleries or vent holes.
If you're taking the cylinders/heads off and cleaning them separately, you could possibly go with soda or walnut shell media and just be 101% sure that everything is cleaned off. Glass can work pretty well too and it doesn't have the disadvantage of oxidizing the alloy surface black if it isn't absolutely completely removed. But you do have to make sure there aren't any beads hiding in nooks and crannies, and they won't dissolve with water. I'd avoid any sand-type material as some of that stuff can really cut, and these alloys aren't that hard.
It is slow and time consuming, but when I decide the cases need cleaning, I get a big pack of green (nonmetal) scouring pads, some WD40 and some brake cleaner, and go to work. If you look hard enough, you can find some of the nonmetal scouring pad material sheets attached on a rotary drill attachment that can help quicken the task on the larger surface areas.
