When restringing, you might try the following:
1. Insert the string into the string-through-body-hole.
2. Grip the end firmly, keep pulling (no need to overdo it), lay it over the bridge (run your thumb over the bridge once while pulling the string), then the nut (again the thumb), then (still pulling) wrap it once around the tuning peg.
3. Release. The string will retain most of it's bent shape at the tuning peg.
4. Wrap it around again one and a half times, then use your thumb to keep it in place.
5. Now insert the string into the hole of the tuning peg. You might have to push the windings down in order to access it.
6. Take a pair of pliers, pull the end of the string through the hole as hard as you can.
7. Still pulling the string with your pliers, tune up a couple steps so it'll stay in place.
8. Tune up.
9. (Hopefully) Enjoy a properly intonating Blackjack.
