I honestly don't know what to say.. because I've heard alot against vibrato in Bassoon, so I havne't really used it at all. But I'd most likely say to use diaphragm vibrato in the high register (Not that interesting in the low)

Personally I prefer the bassoon with some vibrato, particularly in the tenor register and upwards.I think it adds warmth to the sound and can be used to convey greater emotion in the music.Having said that it must always be well controlled and used in the right context.Some music might sound better without it.It must never be used to mask a poor tone quality.That's my feeling.
As far as I know there's 3 main ways to achieve vibrato and I think they've already been mentioned.
1) Lip vibrato which involves up and down movement of the lower jaw.This also changes the pitch slightly.
2) Throat vibrato which involves contracting and relaxing muscles in the throat.
3) diaphragm vibrato which utilizes the strong abdominal muscles to change the air pressure.
I think #3 is best.You can practise it on long notes pushing and relaxing the tummy muscles in a rhythmic and controlled way.Try it on the reed only to start with then on the bassoon.Might sound a bit farm yard like to start with but it'll soon improve.
Best of luck!