Betty Jo, I've used the blue wash out markers a lot, with no problem IF I soak the quilt in cold water, with no detergent, after it's finished. Heat or detergent would set the marks. I think the reason that a thicker point marker is suggested, is that the thinner point ones tend to drag on the quilt and might distort it. I've read in several places that the Frixion pens go away with heat but come back in cold. I don't have any info on washing them out.
Hand quilters use pencil, they mark lightly and use magic to get it out, I guess.
I've never tried that, since I'm mostly a machine quilter.
I'd love to make a whole cloth quilt, I might start small and see how I like doing it before embarking on a big one! Right now I'm quilting the 2011 BOM and it is BIG
Kathy