Never use one of those service station scrubber wands, you don't know what kind of abrasives are embedded in its spongy or squeegee surfaces. Carry your own cleaning materials. You should never use the paper towels at a service station either. Paper is processed wood pulp. Therefore you're scrubbing your windshield with a handful of ground-up tree limbs. Your windshield quickly goes from crystal clear to a pattern of swirls that's especially annoying when riding in the rain or in the glare of on-coming headlights! 

Use a wet, not damp, wash cloth or hand towel. Allow the water to soften the dried-on bugs. Work crosswise and up and down; if you use a circular motion, you tend to increase the rag pressure and scrub harder than you need to. Circular scratches are more annoying to the eye than straight ones. ( don't use diaper material because the tightness of the weave tends to pick up and retain grit.) Soft terry cloth is the best for the soaking and wiping.