I recently picked up my first fretless. A 1985 MIJ Fender Jazz Special. I'm a little ham-fisted right now on it and am trying to get subtle vibrato. I can't seem to get much out of it by rolling my finger back and forth. Sliding it seems to be the only way I can get noticeable vibrato. But then I tend to overdo it.
I realize I need more practice but, is there a trick to rolling your finger or is subtle sliding it the way to get decent vibrato? Do I want to let just the fingertip roll while it sort of grips the string, or do I want a lot of wrist action?
Excuse me if this is a terribly simple question.

You need more of a wiggle type movement. It comes from the elbow, watch some clips of a cello player and you'll get the idea.

You need more of a wiggle type movement. It comes from the elbow, watch some clips of a cello player and you'll get the idea.

+1. Imagine yourself as a cello player. You'll get it. Just be glad you're not a violinist (more difficult vibrato).

while i understand the cello analogy, it's a bit difficult for me to do this. one reason is that the cello player has a beefier neck to play and the instrument is anchored on the floor - it's mroe stable. when i mimick this, the whole bass moves - unless i take my thumb off the back of the neck, but then i lack the necessary pressure to sound a note.

at present, i'm getting vibrato by sliding the string sideways. it works, but not as well. any advice?

Just go with what works for now. Work on what doesn't until it does.

...when i mimick this, the whole bass moves - unless i take my thumb off the back of the neck, but then i lack the necessary pressure to sound a note.

This should not be the case. Assuming you've got the bass on a strap, you should easily be able to stop a note without your thumb. You will never have free vibrato without a good left hand technique, as all (classical) string players can tell you.

In my opinion vibrato is practically an art form unto itself and there are many ways to go about it. There are however, basically two types that most folks identify with. The first is sometimes called “classical” vibrato as it’s what’s used by chamber and orchestral string players, and it involves a kind of pivot action around a note. Sliding vibrato is a kind of exaggeration of this technique and can be very effective in the right circumstances. The second vibrato style has more to do with bending the string and is often referred to as “blues” vibrato.

If the instrument is moving when you’re using classical vibrato, you may be gripping the neck a bit too hard. Try keeping the fretting hand as relaxed as possible and use just the energy you need to get a good tone.

Who else here uses classical vibrato on a fretted instrument? I think it adds a very nice subtle vib.