Just out of curiosity if I was to buy a walnut blaster through bmw to do a DIY walnut blast myself, would anyone else here be interested in 'hiring' it for a fee?
BMW - part 81 29 2 208 034
http://www.minitechinfo.com/tsb/atta...ing_Manual.pdf
Using the walnut method is much quicker and more effective then using a wire bush. One may also think that this would be a safer option as the walnut shell blasting media would simply oxidise upon combustion if it was to enter the chamber, whereas stainless wires from a wire brush could cause engine damage.
This is just a concept at this stage, but please let me know if you're interested.