I posted a similar question on another RV forum and here is what was replied by the members there:
recap of what I've read in the replies:
(in no particular order of preference)
* Dryer sheets (used and wet)
* wet towels on the surface for a bit to loosen the guts then water and a brush
* Blue Beacon truck wash ( but not following a stock truck
* Reliable 1 Spray All purpose cleaner
* Bug Slide Spray
* Superzilla Spray
* Lucas Slick Mist Spray
* The Solution waterless wash
* Bug Scrubber Sponge
* Microfiber rags / towels
* Driving Backward or get a Taller Truck!
I tried the dryer sheets, but they didn't give me satisfactory results.
I purchased a bottle of the Lucas Slick Mist Spray
from a local auto parts store because it was $4 cheaper than Amazon, even when considering the gas needed to go and get it.
I purchased a microfiber bug sponge and with a little effort and judicious spraying with "oil Eater
" I got the front of the rig clean. That stuff will take grease, oil, bugs, tar, those black lines under your windows and most other organics off, if you wait just wait a little bit for it to work.
The front fiberglass surface was pretty dull so I applied the Lucas Slick Mist and shined it right up.
Of course, there were bugs on the front when I returned from a trip to the Oregon Coast. I washed with regular car wash soap from Meguires, and with the microfiber sponge, about 90% of the bugs came off. I sprayed a little more of the Lucas Slick mist and the rest wiped off, No extra elbow grease required.
It may work for your situation as well.
Good luck with your choice.