If you're talking about the crank out awning windows, then nothing- once they pop open after sitting they don't stick until they sit more. If you're talking PH zippers, take a bar of soap to the zippers.
If the glass or metal is sticking to the rubber, try Shenitzu grease. Our Honda minivan sliding door would stick shut and this grease is what the Honda dealer sold us. Apparently dry and or cold will glue the rubber down.
SilVan
Linear Mode
