[Commodore]

Mark IV hit it on the head.
I've been using 'Bon Ami' for years. There is a major misconception that 'Bon Ami' will etch or scratch your glass (Comet, Ajax and Soft Scrub will). 'Bon Ami' does not. Just make sure you do a proper rinse to insure the residue from the cleaning is off the car's finish (it can remove wax). Old fashioned 'Glass Wax' did a nice job between cleanings in the old days. I don't know if it is still available? I'm not in the position to comment on the suitability of 'Bon Ami' for use on a Lexan windshield but would guess that it would be safe. Ask an expert first.
RB