This is the most commonly used false count technique and it will help you perform a large number of powerful packet tricks. It will take a good amount of practice to be able to do it smoothly and reliably, but it is well worth the effort!
This is an intermediate level sleight. It will take many many repetitions to be able to do it smoothly and to make each count look identical.
More Inner Secrets of Card Magic (1960)
Ultimate Secrets of Card Magic (1967)
Issue 4 - Hierophant (1970)
and many other sources