I've really liked writing "Cirque de Halliwell". Since I'm using an episodic format for my series, I can stick with the "highlights" of their adventures. Like three of characters are what I call "insta-siblings", they have inside jokes, they fight, they tease, they're fiercely protective of each other. Instead of describing in detail how their friendship developed over the course of the novel and develop their relationship, I can just establish that "boom" these three are friends. I can use their dialogue and behavior to "show" their established friendship.
Part 3 has also been fun because I can really start to flesh out the characters. I'm starting to explore more of Jamie and Cole's shared history and give the other characters' subplots of their very own.