Where you pick the string is absolutely critical to the technique!

Get used to picking/muting at a point exactly half-way between the bridge and the fret you are fingering. When the tip of your thumb touches the string just after the pick plucks it, you create a 'node' which causes the string to vibrate at twice the fretted frequency. Twice the frequency = a note that is one octave higher.

When you become adept at this , you can try applying the pick at 1/4 of the bridge/fret distance to get a two-octave jump.