I wouldn't say it's an advanced technique, maybe just a neglected one in this age of the Floyd Rose. Like any technique, it's a 2 step process, learn what to do and then practice it, anyhow this is how I do a bend and vibrato, let's use the 7th fret G string bend for an example, the left hand motion is going to come from the wrist and forearm, imagine you are turning a doorknob counter clockwise, it's basically the same motion but smaller, grab the neck and bend the string up by twisting the wrist/forearm, with the string bent to the target note, release the bend slightly, and twist the wrist again, bending the note back to the target, the whole move is the twisting/ untwisting motion, dropping and raising the pitch up to but not past the target note. As you get the hang of it, the amount of pitch you drop will become easier to control and the speed of the twisting/untwisting becomes faster until it actually is vibrato, then you can expieriment with it, slowing it down, speeding it up, wide or narrow , I love vibrato, it really makes the note sing and a good vibrato is something I always notice...........