I'm not familiar with the term "pinch harmonics" but there is a technique that allows you to generate a fundamental and a harmonic, or sometimes a series of harmonics, as you pick the string. As Gidge said, choke up on the pick. What I do is hit the harmonic of the fretted string length with a fingertip (usually a right ring finger or pinky) at the same time you pick the note. Where you pick will determine whether you strike a harmonic because the distance between the pick and your ring finger (or pinky) is very nearly a constant. I keep my right fingers together pretty tightly to do it. It looks like you are hunting the harmonic with the pick, but you're really doing it with the other fingertip.