Carbon Cleaning with Walnut Blasting

[Hammerhead]

I would have to be pretty desperate to walnut shell blast my intake.
IF I was to consider doing this procedure, I'd take it one step further than what Rawze was describing and back off the adjustment of the valves of every cylinder completely and remove the crossheads. That's the only way I could convince myself that all the valves are closed and I shouldn't knock carbon or shell debris accidentally into any of the cylinders.
I'd vacuum out the ports after, before I blew them out with compressed air. I'd be pretty leery of getting something up a valve guide, possible wedging a valve open or closed, so I'd probably do v/g seals after the blasting, and while the old seal was removed I'd blow air down the valve guide before reinstalling the new seals.
This may sound extreme, but the contamination risks of this procedure worry me. I think I'd only perform this as a last option with plans or expectations of an inframe...but I think anybody seriously considering this option is probably in dire straights and can't absorb the financial hit of said inframe, so they shouldn't take any chances and take all of these precautions seriously.