i only wash the fabric when i'm going to use it.
the fabric is treated to prevent mold and fading so i prefer to leave the fabric "as is" until i've decided to put it in a quilt.
once i decide to wash it - i snip the corners off the selvage ends and i place the fabric in a pillow case and tie it shut. then i throw it in the machine to be washed.
then i take the fabric out of the pillow case and put it in the dryer to dry.
when thats done i hang the fabric on a clothes line and spray it all over with heavy spray starch. i have a clothes line in my sewing room that span the entire length of the room.
i let it soak in for a few moments and then i iron the fabric.
now its ready to be cut and used for quilting.