There is a commercial product available to remove marking pencils lines. It is by Quilter's Rule International; they used to have a website, don't know if they still do or not. It worked pretty well for me, when I bought it about 5-6 years ago, and cost was $7.95, but it was worth it to me. I messed up my marking of quilting lines, and this took the lines out so I could start over. Loved it.