I just started using the rain-x anti fog this fall. I am a fan of the regular rain-x for the windshield so I thought I would give it a try.
First make sure you windows are clean to start with then the big thing is to USE VERY LITTLE! spray it on a cloth and wipe the window with that, it will seem like nothing, but it will do it's job. The first time I tried it I did one spray on each side window and two on the windshield, big mistake, streaky, greasy looking, I just kept wiping it every day as it would streak up for about a week with a clean dry rag until it was clear again, now for the last two weeks it has been great.
3 kw solar pv - XW6048 - eight L16's
4 ton GSHP
2003 VW TDI 180k miles - 52 mpg lifetime
evse level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013
@70k miles - 56.56Ahr - 86 SOH - 82.55 Hx - 245 GID