A related question is: What do you use to wipe plastic lens with?
The wrong cloth/towel and cleaner will really swirl/scratch those lens. I am guessing that many a car owner has cleaned their dashboard gauge lens/cover with Windex (or any generic ammoniated cleaner) and paper toweling, only to discover the swirls and scratches induced by such products and methodology.
I have Plexus plastic cleaner and a softer short-nap window-cleaning-type microfiber cloth dedicated for clear plastic only, but it seems my lens still suffer from swirls and scratches. Part of my problem may be in not pre-cleaning them with some type of ACP, as the original poster (OP) has asked about the solution ratio for this cleaning application.