I am really in love with the Pilot FRIXION pen, It apparently was not meant for quilters but we have found it, it is like a felt tip sort of, but when you are done with the marks, you just touch it with a warm iron, and VOILA it is gone. I think it is great.
Someone told me to be careful that when the fabric gets cold it will come back, I haven't found this. .. but so touch it with warm iron again.PS some quilt shops have it , but I found it at Staples.
Rita