Zooming During Live Video... tricks to make smooth?

I realize this is a bit of a “how to” video question… I will often Livestream from the back of a church and this means I will have a long lens on my GH4. Often this is my 100-400mm lens.

I have discovered how sensitive this powerful of a zoom is, so when I’m trying to manually zoom out a little, or zoom in to adjust my framing, it causes amplified movement on screen (my live shot.)

Typically what I do is live switch to a different wider camera while I adjust my tight camera.

But sometimes budgets don’t allow two cameras.

So I guess I’m asking for advice… are there any tricks to adjusting a zoom smoothly?

I’ve seen some gear setups called “follow focus” rigs, but the reviews on cheap ones are terrible. And I’m unsure if spending $350 is any sort of guarantee…

They look like this:

I’m open to any tips or advice?

Thanks guys/gals!