First off, you have to remove the starboard drive axle, which I did. Then, I have followed Oilhammer's advice to remove the subframe to make all access much easier. This made removing the downtube, EGR cooler, and turbo much easier. All of these things create sufficient maneuvering room, although nothing like the unlimited room the BMW owners have.
I bought on craigslist a used 40 lb. device, identical to the BMW video. I have experimentally determined that 1/4" O.D. copper tubing is the minimum size that works with Harbor Freight fine grade walnut shells. Setting the Harbor Freight tank's pressure to 80 lbs. and not opening the bottom media feed valve more that the minimum to get a sufficient, but not over supply of walnut shells works perfectly, quickly removing ALL the gunk and leaving the bare metal showing. There are apparently some walnut shell fines left visible in the joint between the valve and the seat, but I believe a pick can take all of the significant ones out with no problem. I have not yet figured out how to remove the valves in the experimental head so as to be able to determine the actual extent of the gunk removal, but will try to do so over the next few days.
I am doing this planning on having the shop vac and fitting from the bottom, and maneuvering the abrasive blaster from the top, after first insuring that all fluid port openings are protected from dust intrusion.
Franko6 advised me to simply use a torch to burn these ports out. Although I am certain this would work, based on experimenting with my test head, my painful experiences with several house fire events prevents me from being able to manage to do this on the engine still in my car.
Now in my case, I have already removed the CAM for replacement, which means all the valves are definitively closed. Theoretically, this could also be done on any BRM by removing only all the components attached to the stern side of the engine and working on cylinders having both valves closed by adjusting the crankshaft position.
I will be keeping the group posted on my progress. It is heartening to know others are considering this approach.