They’re similar, although with writing you can edit after the fact. There’s much more flexibility with writing. With speaking, you have one shot. In theory, there shouldn’t be any fear in writing as you can write privately. But speaking is a public act.
What kinds of skills? There are many skills involved in writing(a), more skills needed for publishing(b), more skills needed for marketing(c), more skills needed for successful sales(d)., more skills needed for repeatability of (d) (e).
So, for example:
I’ve written(a) and self-published(b).
Bunch of things on Amazon. Conquered that aspect a few years ago.
Marketing was mild as I didn’t care about successful sales or repeatability of successful sales.
My goal was to reach (b) and I did as that is what I wrote for.
But if I want to do writing(a) for (e) – successful repeatable sales, there’s a lot more skills to acquire. There are so many skills necessary that most who reach that level have hired an agent to handle the majority of such things.
The myth of the guy-who-goes-it-alone-against-all-odds-and-is-successful is a persistent myth.
Even when you find successful self-publishing self-promoters, look a little more closely. Which is more the myth: the solitary man or the market?
[my a-e breakdown is my own. I have no idea if it matches up to anybody else’s reality. That’s just the steps I saw long ago and stick with]