I once saw an antique quilt from 1870 in a museum in Ft. Worth, TX, that still had the graphic pencil markings on it, faint, but there.
I have no solution for you, but a suggestion to use a water-washable art pencil (aquarelle) in a med/hard lead to mark your quilts. Those markings, done a little at a time, and not hard/over and over again, *will* wash out. I've used them for years. Google "aquarelle pencils".
Jan in VA