Another way to do it is to press the string down with the first finger or thumb and touch the string with anotehr finger, then pluck with the left hand and slide.
Still another way is to press down the string in the left hand and then place the right thumb on a node, pluck with a right finger and slide.
It is a great sound.
Steve Bailey is the man when it comes to sliding harmonics. He's just sick. If you want to hear some crazy music involving that technique, give him a listen for sure!