Practise playing vibrato at half speed with a metronome. Work it wide and slow, and keep it controlled. Just imagine Yngwie at 50% of the speed, or Friedman etc.. once you get it even then you can work at upping the tempo.
Control is what you're aiming for above all.
Practise things like hitting a note, letting it ring for a beat, then working in some vibrato, bending a note slowly to pitch then adding vibrato etc