I wouldnt do that. Not to my benz. If I did that to my diesel it would kill it. I havent ever done that. Usually the best way to burn off the carbon is to drive 10 miles at 4000 rpm or so. If you do the water trick, let us know how it goes.
I would use a humidifier if I was to do it. An ultrasonic one is probably the best, but dont saturate your air filter with water.