For customer quilts I would use white Miracle chalk in the pounce pad, a chaco liner (white chalk dispensed in a very fine line by a tiny wheel), Miracle chalk mixed with blacklight powder chalk for white fabrics (need to use darkness and a blacklight to see the lines), or mark with a fine permanent Sharpie (let it thoroughly dry first) onto Miracle Film and stitch through it, then tear it off (I attach the Miracle Film with a light spray of temporary spray adhesive. You could also pin it on.)