Delaney started work with Fallout 4 on July 9, 2013. His work consisted of four hours a day for four days then a break for 4, 5 or 6 weeks. This schedule was repeated for two years, totaling approximately 13,000 lines in total.
Delaney had not heard of the Fallout franchise prior to landing the role of the male protagonist. The first line he recorded was "War. War never changes..." while he was unaware this was a well-known phrase within the series, as well as a hint to the scope of the project he was working on.
As he began working on Fallout 4, he purchased Fallout 3. He has joked that he loved the game, but due to his busy life, he "... only made it to Moira's second chapter in her book." On his first playthrough of the game, Brian blew up Megaton, much to the distaste of his coworkers. He responded by exclaiming, "I needed caps, and I didn't know how to get caps. I wanted caps, but I didn't know what caps were!"