You pool cover is meant to collect dirt, leave, and foreign objects before the get into your pool. If your cover has debris on it, it is best removed prior to winding if possible. Scoop up most of the debris. You can then hose it off while winding, there are also good cover cleaning products available, and/or you can pick up the end before the debris falls into the pool (this is what we do). With someone to assist you, wind the cover in most of the way, then grab each corner of the cover, lift it out of the water and fold it over onto your pool deck area. Continue to wind the cover in until you can access the debris and remove it.