I had a local place do soda blasting for an engine block, cylinder head, and some other engine parts. The soda did a great job at removing the carbon from the head. The air cleaner cover did not clean up very well and still had rust around the curled over edge. To clean the parts just use dawn dish soap and water. Was also told it will not embed into the metal. The guy told me that yellow paint was baked on and hard to get off the block.
They also do dustless blasting. I had them do a few parts including the air cleaner. They said it's not aggressive, but was a little shocked to see how porous the metal was after. They said they use sand paper and sand it by hand to lay it back down. They restore cars using this dustless process.
I would advise to stay away from sand blasting your engine block, other engine components,and transmission parts. The sand can get embedded into the parts. Washing and scrubbing won't remove it. Friend did this to his engine and found after a few hours of running it he had a nice layer of sand blasting media in the oil pan.
My experience is to use the soda for the delicate engine and transmission parts. Sand blasting can be used for the frame and other sheet metal parts and castings. This is just my experience with having soda blasting, dustless blasting, and sand blasting done. There are a wide range of different materials available each with there pro's and con's.