I have searched hi & lo and only found info on the Stilo roof. Today was a warm day so I opened the skyroof on my car, it was painfully slow. Last summer it was fine. So i am guessing it needs some TLC. A few squirts of WD40 helped speed things up, so now I would like to know a few things. How can I clean the runners successfully ? Is there a proper way to do this, and if so what grease should I use?