When I sailed as Second Mate we always carried a version of Scotch tape that you can write on with a pencil. For charts that were used often and the DR track was the same, which is commonly the case on a merchant ship, I'd lay out the course on the chart, confirm it with the Master, and then lay a couple of strips of that tape over it side by side. They were just enough for you to plot your fix and easily erasable afterwards.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.