This happened to us a couple of years back. This year we closed the shutters, disconnected the doorbell and pretended not to be home. I am not a grumpy old cow, I had a < 2 week old baby and didn't want to have to keep answering the front door.
BTW Lieferheit window squeegees are in every Manor store. There are ones with a built in spray, and ones with an attachment to reach up high.
For streak free windows you need to wipe the squeegee after every scrape with a wet cloth. For perfect windows, buffing them afterwards with a microfaser cloth works well. You can get these in Migros and they are yellow and can be washed in the washing machine.
Window cleaners cost a small fortune here. You see advertisements every spring for deals for 3 windows for around CHF 120. Counting my windows, my place would cost over CHF 1200. Shutters are extra.