I dunno why anyone would recommend using a vise for this job... and it's more of a knack than a black art.

I can do it easily in my lap with a shifter and cone wrench:

1. Having ensured the spindle will be properly centered in the hub, crank up the locknut against the cone good on one side.

2. Screw the loose cone down onto the bearings. Tighten the locknut slightly onto it; you might want to secure the spindle with the cone wrench on the other side.

3. Use the shifter (or spanner, but I prefer the wide jaws of a shifter) to hold the spindle via the tight locknut, while backing off the loose cone into its locknut until the spindle spins freely. For hollow spindles, keep going until a tiny amount of play appears.

4. When you've dialled in the right setting, crank the loose cone and locknut together and re-check the preload (QR hubs clamped in frame). If you did the first cone and locknut tighter than strictly necessary, you won't need a second cone wrench to loosen it a tad from here if you need to. To tighten it a tad, get a second shifter and crank each locknut together a bit.

Good as gold, piece of piss.