The most common reason people do not start is a belief that they would be bad on camera.
Usually they are right about the first show and wrong about what the skill is.
What it is not
It is not charisma. Some of the best sellers are quiet. The room is not there to be entertained; it is there to look at the thing.
It is not fluency. Pausing while you find the word is fine. Filling the pause with noise is worse.
It is not confidence about value. "I am not sure what this is worth, let us see" is a perfectly good sentence and it is often true.
What it actually is
Holding the object still. More than feels natural. The room is trying to see it.
Saying the specific thing. Not "beautiful piece" — "the glaze pooled here, which only happens in a reduction firing". Specificity is the whole skill and it is purely a matter of knowing your stock.
Answering the awkward question. Somebody asks whether that is a repair. The answer costs you less than the hesitation does.
Repeating a structure so you never face a blank mind. One that works.
Why it is learnable
Because all four are mechanical. None require you to become a different person; they require you to do a small number of things consistently for an hour.
The first show is bad for everybody. The fourth is not.
The thing that actually improves fastest
Watching your own show back once. Ten minutes of it is enough and it is unpleasant, and it will tell you more than any amount of advice — usually that you are going faster than you think and showing less than you think.
More: your first live show.