I think a member on here is related to that guy that owns the firm. The German cleaning companies have apprentice cleaners. The course is 2 and a half years. Learn all the chemicals and methods of cleaning different surfaces like floors etc. When it comes to the window cleaning, they teach them that old method of wet cloth and leather polishing. They even had to use that on shop windows.
May have changed now as I was a foreman at a firm in the mid 90's for a couple of years. A point of interest, the Germans aren't big on domestic WCing. The WFP systems here are years behind the UK, and aren't considered high enough quality apposed to trad.
There are a few Brits over here who are doing quite well out of using WFP to get jobs that are normally left for cherry pickers etc. SO WCing isn't the same everywhere you go.
Good video by the way.