Originally Posted by Alpina_B3_Lux
If you have the correct walnut shell blasting tool then it is actually quite simple from what I have heard. But if you don't, and you have to manually clean every valve from every cylinder with a toothbrush, then it certainly is a pig of a job and ideally needs at least two days (to let the valves soak in cleaning fluid before brushing them off).
I've ordered the BMW blasting tool and will hopefully be able to document how this is done in the next 2-3 weeks or so.
The walnut blaster does look pretty good and would definitely reduce the elbow grease/effort to clean the valves. However you want to make sure the cylinder is at TDC as otherwise it can be pretty easy to fill the entire cylinder with walnut shells. There is no doubt that the blaster will do the job quicker and possibly to a better standard, but depending on how severe the carbon build up is then doing it manually is not too bad. The chemical cleaner will soon loosen up the deposits and you don't need to let it soak for that long.
I'm looking forward to see how your valves look before and after the walnut blaster. The new HPFP and clean has definitely made a big difference on mine. The car feels a lot stronger and I might be looking at a new clutch in the near future as it slipped a bit in 4th after a few launches. Currently leaning towards HPF as I want to keep the feel the same as OE.