C Major uses Scale Form V which involves two squeeze shifts.  After the first squeeze, your hand will be in Position X with 4 on C (2) and F (1).  Both notes are at fret XIII.

When descending, you’ll squeeze to Pos. X to play F on (6) with 4 at fret XIII. 

Review and visualize the scale:

Now practice:

  • Begin with m,i alternation; when comfortable switch a,m (m,a) alternation.
  • Maintain legato connection. When descending the scale, strive to have your left-hand fingers in a prepared posture, hovering near the frets before they play.
  • When secure, practice the scale while vocalizing the note and watching your hands.
  • Finally, play and say the scale one stroke per note from memory.