I use the blue water soluble marking pens, various brands like Clover, Collins, Dritz and they have all washed out with a spritz or two of water. Also the purple air soluble marker works well and disappears on its own or with water. I've also used the Clover chalk pencils which are water soluble, they come in white, blue and pink, but I don't think I've used the pink. They come out. And for dark I use the ceramic chalk mechanical pencils, that can be found by Fons and Porter, Sewline and Bohin. I like the nice fine line they make and they rub and/or wash out. Test on a piece of fabric as already mentioned and make sure it'll work for you.