I use one and swear by it, the lines stay in and no worries about marks washing out etc. They are not all that expensive. Once you have bought one you do not have any other expences for marking your quilt ever again. I find it works best if you just mark up a small amount at a time, say the area you are working on at that sitting. I would not do without mine, so simple and cheap and works like a dream!
Gal