I am using the Pilot Frxion marking pen now. I am using the blue and so far have not had any trouble with it working as told. My DD uses the black. The only problem she had was when she had the marking on over a few days and then ironed it off. It bleached an area on her quilt. But it only happened in one spot. Whether that was a fluke, or because the length of time marked or the fabric we don't know. That has not happened on my quilt. But mine has only been marked in number of minutes. I mark then sew that iron it off, then mark another area and do likewise.
These pens work the best of anything I have worked with so far.