This is a really excellent review.
I did this with a few guys from this board a couple of weeks ago but used a different walnut blaster.
The walnut blaster I used was from Harbour Freight tools for around 20 dollars and was a hand held device with a hopper on top for about $25.
There were a couple of issues with this:
1) The compressor we were using was not of high enough pressure
2) The tool kept jamming (correct non-reused media was in use)
3) It was difficult to get the tool to Cyl 6 as the space was limited
4) It makes a hell of a mess
That said I did feel that it accomplished similar effects but just took a lot more time - and a lot less money.
I would personally recommend that for 1000 USD if more than two people want to buy it, it becomes cost effective as dealers charge around 500USD for the service.
2008 E92 335i