I have a bit of a problem with string bending, say i have to bend the string back and forth between the 5th and 7th frets about 4 times. on the third time i lose alot of sound, by the fourth there is no sound. any tips on that?
I also am finding it hard to vibrato when i bend. any help?
because bending over and over kills your sustain.

Pluck it agian right before you bend it back up or it'll fade out.

You can't really vibrato while bending, cause vibrato is like minute rapid bending.