He says he always liked comics and cartooning, and recalls being impressed when The Wonderful World of Disney showed the animation artists working behind the scenes.

He cites other artists in addition to Frazetta as inspiration: Alex Raymond, Stan Drake, Leonard Starr, John Prentice, and Al Williamson.

In his late twenties, Manley would have the opportunity to work for a brief but intensely formative time alongside Williamson, in that artist's Honesdale, Pennsylvania studio.

[7] He has also contributed to other comic book titles such as Batman, Quasar, Captain America, Marvel Universe,[7] and The Power of Shazam!.

[8] His extensive bibliography in comic books includes a large number of short runs and fill-in issues on a wide variety of titles.

Throughout the 2000s, Manley created storyboards as a freelance artist on TV cartoons such as: Samurai Jack (on which series he also received two writing credits); Kim Possible; The Fairly OddParents; The Venture Brothers; Growing Up Creepie; and The Secret Saturdays.

Other projects in this period included: Spy Groove for MTV;[3] Spawn for HBO; ABC's One Saturday Morning; Clerks: The Animated Series, based on the Kevin Smith movie; and Justice League: The New Frontier.

Manley also co-produced a how-to DVD along with Danny Fingeroth, How to Create Comics from Script to Print, also distributed by TwoMorrows.

Manley was hired to draw the serial newspaper comic strip Judge Parker for four weeks beginning March 15, 2010, filling in for regular artist Eduardo Barreto during an illness.

In late March 2016, it was announced that Manley would succeed Paul Ryan, who had died unexpectedly, as artist on The Phantom daily strips (the Sundays would continue to be drawn by the incumbent, Terry Beatty).

[15] Manley noted that he and Paul Ryan are numbered among a small and notable group of artists who have professionally drawn the adventures of both Batman and The Phantom.