Isaac Clarn is of the Specialist Occupation, someone who focus on various Duties related to Tech, Vehicles, Engineering and rarely as go-to Historians. In this Case, Isaac Clarn is primarily a "Techy". Knowing things like Hacking, Coding, Web Design (far stretch) & Understanding the Basics of how Power/Gigabytes work. However, as a Soldier of The Warrior Corporation, he too know various Military Skillsets, that being Small Arms, Automatic Weaponry & Close-quarters Combat. 

For his Voice, a General if not Boring Middle Aged Man will do just fine. I could link Examples, but I feel for such a Basic Voice, it's Unnecessary. Just do what you want/can do in any format you want. (ABC, AAA, BBB, CCC, Etc.)