Often working with super8 and 16mm, as well as various video formats, Armstrong frequently uses hand-altering film techniques, employing bleaches, dyes, scratches, and paint to alter both his own footage and found films. His works have been screened at various galleries, during live performances and in traditional cinemas worldwide. His films are influenced by filmmakers as diverse as Stan Brakhage, Hollis Frampton, Bela Tarr, Alexander Sokurov, Guy Maddin and Andrei Tarkovsky.