I'm pretty okay at vibrato/fast string bends, but somehow I feel that my technique is sloppy and I know there's alot of room for improvement. For instance, in songs that use fast string bends in solos, when I transition between strings or notes, I have trouble instantly going into the vibrato, it's as though I have to have my finger secure on the fret beforehand. Also, my fingers tend to be....almost perpendicular to the fretboard, for lack of a better term. I mainly use my middle finger though I've been slowly trying to use my index finger, and I'm getting a little better at it. How does one practice vibrato? What can I try to improve my technique?
Slow right down until you can play it perfectly, then gradually up the tempo.
Try applying less pressure on... hm... forcing your fingers on the fretboard. Rather try to use just as much so it is stable (the string) on the fretboard and apply pressure by pulling/pushing the string up. I base my opinion that you apply too much pressure on fretting the strings because the way you described it is the way I felt while I myself was pressing the string down as if hell was after me. Perpendicular fingering when not playing chords means too much force. You're not raping the guitar, you're playing on it, your fingers should be like the wind.