I clean my visor with a microfiber cloth and Armor-All (or equivalent). No scratching, no harsh chemical, a well-lubricated surface... The slight, slick residue helps prevent other bugs/debris from sticking in the future. There were three miracle chemicals produced in the last century- Armor-All, WD-40, and silicone (glues/sealers/lubricants/sex toys).
So, what part of "clean" goes with "residue"? Seriously, how do you get that Armor-All crap off?