I've tried a number of methods of marking and the one I like the very best is the Crayola ultrathin washable markers. Certainly the price is right and they are commonly available for purchase in an assortment of colors. They leave a nice mark, stay until you are ready to be done with them. I have not had any problem with them not washing out. I suppose the only thing I might not like about them is if I didn't want to launder the quilt when I've finished the quilt. Keep in mind that the markings don't come out with a spritz of water--must be actually laundered.