I agree with Tallchick - there are no rules.
This is THE number one reason I bought a Speed Queen washing machine. It fills with water all the way to the top. I wash my king-size quilt (wool batting) with cool water and regular liquid detergent (I found powder doesn't always dissolve 100% in cool water). I have a bulky/bedding setting on the washing machine, SQ describes it thusly: "Items like comforters, pillows and rugs are bulky; they need a cycle with extra water to really soak in and clean them. The Bulky cycle does just that. And, it uses a slower spin speed to help ensure your drum doesn’t get unbalanced." Once the cycle is finished, if I find the quilt is too wet for the dryer, I'll adjust its position in the tub if necessary, then do a "drain and spin" cycle to spin out excess fabric. It then goes in the dryer on low for 30 minutes, shake it out, dry another 30 minutes, etc.