I never agitate my quilts. I fill the machine with water and detergent, add the quilt, squeeze the water into it and let it soak for 30 mintues. Then, I advance the dial to spin, and repeat the steps on the rinse cycle.
I also would never put a quilt into a dryer. These machines are very hard on fabrics...the lint you remove from the lint trap are fabric fibers, you know! I have a 5-line clothesline...I drape the quilt evenly over all 5 lines, face down so that the sun will not fade the top (even though the clothesline is in the shade most of the day. If it were in full sun, I would probably throw a clean sheet over the quilt.)
You have spent all that money and time making a quilt, you should care for it as well as you can!