I don't pre-wash. Just put it in its color-coded bin when I get it home as it awaits its quilting fate. I've had virtually no issues with bleeding or weird shrinking when I wash the quilted items after completion. And I've even used quilting flannel in quilts and as backings, and I love bright colors. I've only pre-washed one time when I made a red and white wedding quilt for my daughter. She wouldn't have been happy with pink.
When I use the fabric, I steam out any wrinkles. Usually only use starch if I absolutely need to do it.