I know we've talked about this before. But, after a particularly tough lesson with a student, there are some more points I wanted to add.



For bending and vibrato, I always wrap my thumb over the top of the neck. And I pivot on the side of my hand, where the index finger meets my palm. It's a wrist and elbow motion. Not a finger motion.
And I try to reinforce my bends/vibrato with as many fingers as possible. For vibrato, you may try bending the string down towards the ground first, then up. This is usually good to get you used to NOT using your fingers. It's kinda like shaking a locked doorknob.

Keep your points of leverage: Keep your Thumb over the top of the neck. And keep pivoting on the side of your hand, right where the Index Finger meets the palm of your hand. This is the "Fulcrum" that will help you get the proper leverage. Maintain that contact. If your Fulcrum isn't in contact with the side of the guitar's Neck, you will lose this leverage.

For bending, it's the same motion. For accuracy, I often play a note, then try to match it with a lower, bent note. Try the Am Pentatonic scale, at the 5th. position. Play the G string, 8th. fret. Now bend the G string, 7th. fret to match it. (Use your ring finger, reinforced with your middle finger. Keep your thumb wrapped over the top of the neck, and your Index Finger on the B String, 5th. Fret. This will help with your technique).

Next, play the G string 9th. fret. Bend the G string, 7th. fret to match it. Continue with higher frets on the G string. Each time, bending the G string 7th. fret to match it. I can usually get 2 1/2 to 3 whole steps (5 to 6 frets), higher. Then I run out of fretboard, as the G string will get pushed off of the top of the neck.

The whole thing is accuracy, and control.

You might start with 1/2 step bends.

Try bending down towards the ground, first. Also concentrate on releasing the bend, back to the original, non-bent position.
Now, try repeating the same bends, but up, towards the ceiling. Still working on the pitch, as well as the release.

When you can do both motions, try combining them. Down to pitch-release-up to pitch-release. This bending and releasing motion is the one you'll need for Vibrato, also.

Don't let your fingertips point up or down. Keep them pointing at the fretboard. If they point up or down, you will lose the pressure needed, to keep the notes ringing clearly.


It takes a long time, to really feel comfortable with it. And it's a pretty burly technique. So, work for 5 minutes or so, and take a break.

Using the reinforced fingering, and the larger muscles of your forearm are some of the main reasons why this type of Bending and Vibrato will give you more control, accuracy, and tone.
If you were to use only the little muscles of your fingers for these techniques, you would not have the control to really get the most from them. Or, the endurance. You may even hurt yourself.


After having to explain this so thoroughly the other day, I realized the added info may be helpful.

P.S.
If I'm doing a 1st. finger vibrato, I throw my elbow way out, to get that knuckle/fulcrum working.