I started using a product sold by Griots Garage called Speed Shine, at first on the bike to clean it up after a ride. Then I tried it on my helmet and face shield and have been using it for two years. It removes bugs quite well and leaves no streaks or smears, unlike other plastic cleaners I had tried. I keep a small, maybe 3 ounce, sprayer of it and small micro fiber cloth in my tailbag and clean the shield if I get one of those big goobery bugs right where my eyes are trying to focus. Cleans the bike and helmet quite well and leaves a shine that makes subsequent cleaning much easier
Griots Garage Speed Shine
I like this company's products. I use their rubber cleaner, wheel cleaner, hand polish, hand wax, and clay bar. Their vinyl and rubber dressing is expensive but so much better than Armor All and the like that I use it exclusively.