Start by being an arrogant jerk. Be mindful of the arrogance, "Man, I'm an arrogant jerk," and be humbled. Let that humility disintegrate into low self-esteem and, being mindful of it, learning the capacity to smile despite the circumstances. Eventually, the oscillations will decrease, and rather than switching between arrogance and a lack of confidence, it will settle in humble, unshakable faith. Faith in truth and one's own abilities. It is also valuable to go through existential crises along the way, like asking the ultimate nature of truth itself, discerning how meaning arises from words, how experience arises from thoughts, and how logic arises from feelings.
That's my experience, though. Maybe yours could be different. In my experience, skeptical doubt is removed slowly over time rather than instantly. It is removed by avoiding the extremes of doubt and pride: doubt in self, doubt in the dhamma (lots of people on Dhammawheel can help you with this), pride in self, and pride in the dhamma.