Confidence is a tricky thing for a lot of us. For one thing, it can be situational. I can cook and bake but in a narrow range. So I feel confident within my comfort zone. My bad dream would be finding myself on the Great British Baking show. I’d run for the exit before the hosts could assign their first challenge.
Confidence can be dependent on how practiced the skills are. I could hand reef and steer quite well at one point. Add to that some coastal piloting skills and basic knowledge of celestial navigation. I was not an expert, but no slouch either.
Then we can enter the realm of things that never seem stale. Bullshit; I mean the ability to sling it, not the real stuff. My skills may be limited only by my sense of ambition, your gullibility, and my general knowledge of the topic area.
I have trained with some of the best: con artists, creative confabulists, professors of anthropology, master mariners, folk singers, journalists, and politicians. I have found that the more diverse your foundation, the better off you are.
So it’s no mystery that BS artists with significant confidence levels must study widely. I strongly recommend in-person tuition over watching movies, TV, or reading books. So much of the gestural and verbal nuance of laying it on with just the correct level of thickness only comes from personal, up close observance.
Good luck. And remember to practice lots!