Going through some old drafting tools and supplies and found an Alvin Dry Cleaning Pad (35 years old) that we used to keep our drawings clean and remove smudges. I tried it on some Veg Tan pencil lines and did a good job of removing the graphite with minor effort. Alvin still sells them and are relatively inexpensive . If not familiar with them , they are a small soft cloth bag filled with gum eraser dust ( dust not chunks) that would be dusted on your drawing to keep it from smudging while using your t-square's etc. or use with the cloth bag as a gentle eraser.
Reading current reviews online it appears many use them for cleaning many different items
Thought I would pass this on -Thanks