I use muslin all the time that I get from Joann's. It works fine. I do not prewash until the quilt is finished. I have a quilt that I made in 2000 that is on my bed from November through March every year, and the only thing that is showing its' age is the bindings. It has been washed at least once a month each winter for 12 years and looks amazing. Over the summer, I will replace the well-worn bindings.