to focus on something like vibrato learn to sing WITH vibrato.. you will KNOW when you are alone that the way you bend the strings may not be correct. Slowly focus on every micro movement needed to be made to emulate this smoothly.If its a quick one be smooth,if its a slow one be smooth. The start and end point of the note you are applying vibrato to must lie in the scale of the lick you just played.Practice,focus and self criticism is a must to master this.