Yes, it is better to have the signatures done before the quilt is quilted but I'm assuming you have the quilt already finished and now want the signatures.
I have no experience doing this but I do use the pigma pen for making labels and would use one with a fine line to avoid "smudging". I wonder if you can put the quilt into a frame/hoop to hold it taut while the person signs. I think I would try that to see if it would help; otherwise, I think it's going to puff up and make a mess of things. Perhaps have a sample piece available for the person to practice before actually putting their signature on the quilt itself so they have an idea how much pressure to use and how quickly to move their hand. This is more like drawing than actually signing.
Some signature quilts have the signature embroidered. Perhaps this might be of use for you, being sure the stitchery only goes through the quilt block and not all the way through the quilt.
Good luck!
Last edited by illinois; 06-21-2022 at 02:27 AM.