While it may be safe, it’s not something that I personally would use. Dusters typically use some kind of parafin wax in their fibers to catch debris. This debris will stay in it and you could potentially do more harm than good by continuously dragging abrasive debris across the surface of the car. When people ask me what to do with the car between washes, I simply tell them that I always take the safe route, and let it get dirty until the next wash.