Trim the tubing to fit and expose the pencil tip. I marked one here with white tape to make it easier to see in the dark. The final pencil is 4x60mm - it will fit inside even the smallest survival kit. A sharp blade (which MUST be in any survival kit) can be used to keep the tip exposed and sharp. The tubing also keeps the lead in one piece should you accidently drop it.
Coloured or luminous heat shrink tubing would help make it more visible (here