Prisma Color VERITHIN GOLD is one pencil that COMPLETELY rubs off or washes out.
Use a light hand, when marking, and the gold usually wears off before you are finished hand quilting.
As a hand quilter over the years, I learned the hard way. I have tried every product available.
If you use markers, you are adding acids to your fabrics that will break down the fibers in time. If it is a dog bed or wall hanging
who cares, but for an heirloom like your DEAR JANE, THE ONLY reliable products I would use are
Pat Campbells White chalk Pencil, soap, or soapstone on darks and a
Prisma VERITHIN color GOLD on lights,
or a HERA on any fabric you can see the indention, as someone else suggested.
To test my suggestion, cut a couple of squares of batting and bleached muslin and make a quilt sandwich.
Use a Prismacolor Verithin GOLD pencil to mark a design. No doubt, ff your Mom used pencil, she may have used a type that was pure graphite, not the ones found today that have chemical additives. These pencils will not wash out. I have a queen size quilt with the marks still in it after many years of washing.