only use silicone spray with ptfe. spray a very generous amount in both window runners. if you wind the window down you can spray it in at each side, then work the window up and down until it regains normal speed. you may find any excess spray leaks out the bottom of the door, dont worry it will stop once all the excess drains away, you need to spray that much to get the dirt out of the runners.
DO NOT use any oil based lubricants such as wd40 becasue that will make them worse in the long run.