Yeah you picked another tough one - also on my to do list for years What helped me in this case was to decide in advance how many “oscillations/mini bends” I would include in each (vibratoed?) note, and what their rhythm would be. So the vibrato is fully planned and can be practiced consistently: I decided for two oscillations of the first note, and a single one for the second which is pretty much just a bend.
Actually I started doing the same for left hand trills: rather than hammering/pulling off randomly like a madman, which caused me a lot of fretting hand tension and loss of control, I now try to do it with a specific rhythm and a specific number of notes.
Of course this is just my way of doing things which is quite mathematical/academic, I’m sure there are players who can just do these things by intuition.
@lars, it’s interesting that we have opposite experiences with the swipes: for me a swipe is a very simple right hand movement with quite a lot of margin for error, provided that the left hand is muting well. TWPS feels a bit more like walking on thin ice! Maybe this is due to our different choices of picking mechanics?