I am glad to have found this thread. I agree that there should be some more overt means of setting car wash mode that is less like needing to know a hidden move in a video game. It is too easy to mess up the procedure if the owner doesn’t inform the wash attendant or the attendant is distracted from following the procedure.
I believe it would be a good idea to add an info pane that can, and probably should by default, appear on the home screen of the infotainment system. The pane should have a slider that allows setting car wash mode. It would be easy for both the owner and wash attendant to see what mode the car is in. For safety, the car wash mode could auto cancel after 15 minutes. Again, it would be easy to see the car has reset the mode.