Fast Fingers

Thief looting is unlocked by completing the second set of Thief Guild challenges not to be confused with manually looting the guards you kill. Once hired, the thieves will steal from the civilians around you and any dead bodies that they come across at a relatively quick pace. Simply hire thieves before entering a major conflict in a sequence or another method is to find a large group of guards like in the Janissary camp for example, lure them together and use Arrow Storm. They will loot all the bodies for you, simply rinse and repeat.