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JustinGuitar.com has a video - he keeps getting mentioned as a good on-line guide for how to do things.
I won't tell you what I do ... best you don't copy my mistakes.
I find vibrato with no bends hard enough.
Had to laugh at the way Justin explains it all so well and then, at speed, he simply shakes the guitar. I tend to use the violinists method of a vibrato by moving the pressure forward and back (not side to side) as it gives a fuller up and down pitch change. Or I use a guitar with a whangy bar, like Gilmour.
It works for me but I'm thinking about it on a Gibson scale neck with fairly light strings (9s). I wouldn't try it on an acoustic and my only longer scale guitar has a Floyd anyway. At least its not a commonly used trick. I can never get my head around how you bend a harmonic and apply a bit of vibrato. Closest I can get is to grab the whangy and shake the guitar up and down
My tips for the sideways approach would be to have the thumb resting over the top edge of the neck, and to think of this as a pivot point, around which the rest of the hand turns. Then keep the wrist more or less locked/immobile, and turn the whole forearm/hand as a unit - that way, you are using bigger, stronger arm muscles to get the bend and/or vibrato. I'd say practice both bends and vibrato separately using this technique first, and then when ready, try putting vibrato on at the top of a bend. It does take time and practice before the results come (at least in my experience) but if you stick at it, it will start to happen. I can even do bending vibrato on guitars fitted with 12s now, using this approach.