First make sure your hands are clean as you do not want them to leave a mark. Use a good quality Fabric Eraser gently, work on a hard surface and keep the quilt taught where you are working and be very careful not to pill the fabric where you rub. Use a good light and brush away the rubbings as you go as these tend to wear the fabric. Lastly a light dubbing with water only not allowing the fabric to get wet. I work in Gallery Conservation.