I soak both fat quarters and jelly roll pieces. I don't want to go through all of that work and find that something bleeds. Rather than washing and drying pieces in your machine (will fray terribly), just soak pieces in warm to hot water for about 20 minutes. Take pieces out of machine, squeeze out excess water and let dry on drying rack. This also helps with preventing shrinkage which can cause pieces to pucker later on.
Arlene