Quilt guild a bnch of years ago said use "naptha soap" (none of todays chemicals) that you can buy on the web or an old 5 and dime! Use a potatoe grater and then make a paste and they sugested in the bathtub or soak in the washer with no aggitation and the gentlest spin just enough to be able to get it out of the tub without all the water weight. Then hang it outside. These ladies were saving and recovering old linens and quilts old white gloves (a little easier to play with). Good luck that is an awesome quilt!