This was discussed a month or so ago in another thread... I'm sure our gracious mods or someone will eventually post a link, but the gist of it was that rain-x anti-fog says specifically on the bottle that it's for glass - not for plastic. Which I can verify cause I've used that and regular rain-x for many years.
[edit: what the heck... I'll do it: click me, and me]
[edit: what the heck... I'll do it: click me, and me]