Theres multiple ways, quite simply he did it in the video with the pitchbend, the video said he was using reason, so im pretty sure he had those vocals loaded into the NN-XT sampler, played them out and used the pitch bend for the slow down effect. In protools if u have it use Vari Fi.
If your using a VST based DAW use TAPE STOP its free and i recently posted up a link on how to automate it correctly. In another thread.
Theres hundreds of ways to stretch the vocal/speed it up, u can simple use time strectching in any DAW, if you want to do it that way and you can also use the tune button in samplers such as kontakt or NN-XT for the pitch. Im sure there is tons of youtube videos on this.