We have a miele perfect clean oven and are not sure how to tackle the cleaning. I have read on the internet that these ovens are really easy to clean (clue is in their name) but I haven't found this to be the case. Is just soap and water ok, or can you use special oven cleaners? I'm scared i'll damage any special coatings and be a few hundred CHF out of pocket as a result. Any tips on how best to clean one of these ovens?