What is the trick to make bugs removeable from a vehicle?

We spend a large portion of our year in warm dry climates and I assume that is something that flying bugs don't like because I don't have a bug problem there. But summers are spent in WY and I swear I get bug splatter on my rear window backing out of a parking spot. We have a new car and I don't want to ruin the finish with brillo pads. There are bright yellow bugs and some so darn tiny that they just make a pimple on the finish. I've started using WD 40 to remove them and to put a protective finish to the front end. Whats the trick?