That tutorial I made was not designed to give the results of "real flickering fire".
It was merely a tutorial to show how one can "steal" default effects components for your own use.
It is using the default "fire" particle type (cloud), and because of the nature of the software-cloud particle type, you will need to tweak the look/motion of your (particle) shape and emitter to get a better, faster fire flow.
You could always map footage of real flickering fire onto sprites, and change the cloud particle type to those sprites, and you should have a better look to them.
Did that help?
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS