Thumbs and Marked Pencils.
Xercules,
Curiously, this is the first I've heard of your magic pencils (just shows how far ATC was (is) divorced from reality !). However, it shows how Great Minds, as ever, Think Alike.
I take it that these would only be used in the Flight Planning Room. If, however, you took them into the air to use:
How did you tether them to you (on a piece of string ?),
If they weren't secured, what happened when you dropped them down the bottom of the cockpit ? (apart from the whack on your bone dome which bid fair to compression-fracture a cervical verterbra or two).
Did your instructor then invert the thing and pick it off the canopy ? (this actually happened to me once in a Harvard in the States).
All shows the innate superiority of the Thumb Method.
Cheers, Danny.