I had been struggling trying to find a marker, pen pencil that would show up good on the fabrics. A coworker that also quilts told me about Pilot Brand Frixion Erasable pens. Said she got them at a quilt show however, Staples also carries them (I'm sure other office supplies places do also. I got the 3 pack last night and I have to say I love these things. They make a nice clear crisp line that makes it easy to hand quit. Then the lines disappear when you apply the iron. They also have a 6 pack , 8 pack, single and double (Single and double only are in black) But I have to say I love these things. I have purchased a ton of pencils, and markers and none of them work that great or the lines are real light and smudged and with hand quilting I felt I needed that nice crisp line to follow.
I tested them on several pieces of fabric last night both light and dark and gone as soon as the iron touched it.