We use a ladder and a long handled windshield washer like they use on the 18-wheelers. We use soap and water and the nylon side of the washer, not the rubber squeege. This gets the bugs off. We are careful not to scratch the fiberglass.
Our cabover is on a C-5500 Super C, so it is REALLY up there and this works for us.
2006 Fun Mover RV on a C5500 Kodiak chassis with a 6.6L Duramax LLY and Allison 1000 tranny, remote door locks, Steer Safe and Henderson Rear Trac Bar