If I run into cloud of lovebugs the visibility through my Shoei's shield will drop to nil within a matter of minutes. To clean it I'll pull into a gas station, wet a paper towel, and lay it over the shield for a few minutes. After presoaking the bug splats, I gently rub them off with another soaking wet paper towel saturated with liquid handsoap then throw the towel in the trash, and wipe the shield again with another new wet paper towel with no soap. Lather, rinse and repeat as
When there's no soft cloth of microfiber available, plenty of water, plenty of fresh paper towels, and being ever so gentle while wiping is the key to getting a crystal clear shield with nary a scratch.