Barrowing from Jon’s idea I picked up my guitar and watched how my fingers moved. Once my finger is on the string and it’s ringing, I just push or pull to make it move, but my finger tip does not roll on the string at all. The angle of the tip of my finger to the neck never changes in relationship to the neck. So my top knuckle never moves and the bottom two knuckles do the moving of the string. Make sure you are pushing down on the string as you are pushing/pulling.