Another thing that works well is wet newspapers. I learned about that when I owned an airplane - one needs to be careful cleaning the plexiglass windshield and windows (very expensive!) and when I had a motorcycle with a plexiglass windshield, I'd wet newspapers to just shy of dripping wet, let them sit on the windshield for ~20 minutes, then just wipe the bugs off.
Of course your hands get black with the ink but it washes off easily enough with soap & water. For some reason the ink doesn't stick to the windows. I never found an easier way to clean plastic windows without scratching them. Note carefully though that the newspaper must be wet.
