Aside from the excellent interviews by Midnighteer Robert Mitchell, which you can watch here, we've found an interesting interview with What We Do In The Shadows' Jemaine Clement (and Stu!) by Cate Kustanczy at Digital Journal. Kustanczy provides a nice in-depth look at the film.
Owing to the improvised nature of the shoot, it took close to a year to whittle Shadows’ 125 hours of footage down to a 90-minute running time. Stu Rutherford, who plays a human friend in the movie (echoing his real-life, long-term relationship with the filmmakers), recalls doing 14 takes for a scene in which the vampires meet their nemeses, a local werewolf gang, the head of which is played by noted Kiwi actor/comedian Rhys Darby. “I was only there on the edge (of the scene), but thought, this is going to be a problem with the edit,” Rutherford recalls. “Every take had weird tangents and people standing in different places. It was like, wow [...] I know their editor, and thought, ‘This might be quite a nightmare...’”