Spray the inside channels(one at the front and one in the rear of the door), and the mechanisms with silicone spray. Sometimes a little bit of candle wax rubbed onto the panel channel that rubs against the glass solves the problem.(or like was suggested in the other thread, waxing the inside of the glass.) The wax doesn't leave any residue after for stuff to stick to, to scratch the glass when being moved up and down.