I don't know how John does it, but I can tell you how I do it.
The author in the book (and some folks here, as well) used a Lyman "M" expander die. This is a parallel-sided plug that opens the neck up wide enough to accept the bullet base. They are caliber specific. Lyman developed it for cast bullet shooting where any scoring of the bullet on seating would have a detrimental effect on accuracy. I used them many years ago for cast bullets but didn't like the way the brass was "worked" at the case mouth. I next switched to a RCBS Neck Expander die which uses a separate plug for each caliber. The RCBS plug has a longish, parallel side that progresses into a trumpet-like flare. You apply as much flare as you need to get the bullet base into the neck. I liked these but they were pricey to operate if you shot a lot of different calibers as, like the Lyman, you needed a new plug for each new caliber. When Lee came out with their Universal Neck Expanding Die I tried it. Two plugs cover all bullet diameters from 22 to 45. The plugs have a long, gentle taper that is barely perceptible when used properly. I have found them to be superior to Lyman and RCBS. It only takes a light touch to flare the case mouth enough to seat the bullet base into the neck and does away with the need for those brass-thinning VLD tapered reamers that Lyman and others sell. It also allows you to simply, lightly, deburr the case mouth after trimming instead of a heavy "chamfering" to aid in bullet seating.
And a light touch is all you need. Just enough to slip the first bit of the bullet base into the sized neck. Now, to use this technique to any benefit, like crimping**, your brass must be all the same length. At every reloading I trim my brass to the lowest common denominator (shortest case in the lot) for uniformity in flare and, later, crimp if I'm using one.
What flaring does -no matter which tool you use- is to start the bullet straight into the case. No shaving copper jacket, no "thump" as the bullet enters the case mouth. I was loading 6.5x55 yesterday and noted that the bullets seated so smoothly in the flared cases that it felt as though the cases hadn't been sized. The difference is startling. For those who shoot 22 Hornet and get tired of seeing the bullet bulged off to one side of the thin case neck, flaring is the cure to that misalignment.
And with better alignment comes better accuracy. My Hornet is a half-minute rifle and the 6.5 delivered several groups in the .2 to .3" range yesterday. In my added opinion, it works.~Muir
(** Crimp: Another good accuracy tool)