An easy way to get those flies of your windshield and your paint is:
put a wet newspaper on the paint (or window) and let it there for about half an hour. Keep it very wet. After removing the newspaper they come off much easier.
Second:
After WW II the americans GI's brought the Nylons/ladypanty's to europe. These nylons are nice tools for cleaning the flies from your window or the paint. Use much water.