I tried a soft gum eraser but it didn't lift much pencil off so as my husband had gone over the mountain to town I asked him to pick up a fabric eraser from Joann fabrics.
Works a treat, your advise for method is perfect Merivale. You were also right about the rubbings - they do wear. Found out the hard way! Most marks are now gone but I soooo appreciate everyone's advise as there are so many pencils, that do not disappear as they advertise beyond the soft lead pencil on my quilt.
This has been a really scary experience for me and I want to thank you all again for rallying to help a struggling quilter.