I bought an inexpensive portable media blaster from Harbor Freight a few weeks ago and finally got a chance to use it last night. First, it makes one helluva mess. Second, with some tweaking and practice--in other words, kinking the feed line a bit and bumping the hopper regularly to keep it flowing--it really works well.
I played with the left engine case and one of the rocker boxes. It didn't do too well up against oil/dirt build up, but removed corrosion like a pro. I'll scrub off the oil gunk later and hit them again. After that I'll primer and paint them to prevent further corrosion.
Respirator and goggles are a must!