You could also try the classical style of vibrato, which is more a horizontal movement that the vertical wide rock vibrato. It's easier on a bend, and gives the notes a kind of 'shimmer' rather than full on vibrato.

I personally quite like the subtlety of it, but it's all down to taste...

It's all in the wrist ;)

Also, in addition to CW14's suggestion above of bending to a note a tone above the one fretted, I'd go for different increments as well. Try bending a note to the pitch of 1,2,3,4 or whatever frets higher - focus on accuracy and executing it at different speeds....