There are a number of things to consider or try:
- Do not use hair spray as it may stain the fabric.
- If possible test any method in a low visibility are of the fabric.
- White Gum Eraser.
- Detergent and a soft bristle brush.
- Baking soda and a soft bristle brush.
There are also ways to mark that are easily washable. Checking in at your local quilt shop to find alternative marking tools and pencils can be the best option for the future.