In 1995, he began working with Marvel, penciling the Ultragirl miniseries.
In 1997, he began a long association with DC Comics, beginning with a nearly 60-issue run on the Peter David written Supergirl series. Following that, he penciled the Dan Jolley written Bloodhound, which was canceled within a year.
In 2011 Kirk began a run on X-Factor, reuniting him with his Supergirl collaborator, Peter David, penciling issues 225 - 228. Kirk would return to that title with issue 233, and remained the regular penciller on it until it ended in mid-2013 with issue 256. David has named Kirk one of the three artists whose art has mostly closely matched the visuals he conceived when writing comic book scripts (the others being George Pérez and Dale Keown).[3]
Hell Comes To Birmingham (collects Captain Britain and MI: 13 #5-9, 120 pages, Panini Comics, June 2009, ISBN1-84653-423-2, Marvel Comics, July 2009, ISBN0-7851-3345-3)
Vampire State (collects Captain Britain and MI: 13 #10-15 + annual #1, 184 pages, Marvel Comics, October 2009, ISBN0-7851-3952-4)