How do I do the infinite ammo glitch?

A glitch or exploit that I often see in speed-runs somehow makes it so that weapons don't cost ammo to fire. How do they do that?

(1) Wield a Vladof rocket launcher.
(2) Fire it until the next shot is a free shot (i.e. won't cost ammo).
(3) Switch away from the Vladof rocket launcher (without using the inventory menu).
(4) Before the animation of pulling out the next weapon begins, change the Vladof rocket launcher's weapon slot position (in the inventory menu). Thenceforth, weapons will cost one less ammo to fire until you wield the Vladof rocket launcher again. The glitch is also known as the Vladof rocket launcher glitch for the obvious reason.

I suspect that this glitch is doable with other weapons that have an identical effect. This seems to be a subset of what has been called the "weapon merge glitch", because other glitches exist with identical methodology to apply the special effects of other weapons to other weapons. I confirm that following these steps with Bane or Morningstar causes effects of these weapons to be applied to other weapons wielded, at least Bane's firing sound effect and Morningstar's weapon-switch sound effect.

Which version of Borderlands 2 am I confirming this on? The bottom-right corner of my Match browser/Online Games menu says, "Version 1.8.3". Otherwise, "Details" tab of the "Properties" of my "Borderlands2.exe" file: "File version 1.0.29.41124", "Product version 1.0.29.827556", and "Date modified 2014-07-15 22:59".

Apparently, it is also possible to "stack" the effect at-will so that even weapons that consume greater than one ammo per pull-of-the-trigger may have their ammo cost reduced to 0 as well, but stacking only seems possible before version 1.4.

Update: ProfessorBroman explains the glitch more in-depth here. He's a Borderlands 2 speed-runner who uses glitches extensively, so I trust his theory. In summary, on the latest patches, the glitch cannot reduce ammo consumption by more than one, and other entities using Vladof rocket launchers can unset the effect.

Update 2: While the AGDQ 2014 co-op speed-run demonstrates this being done as non-host, I was unable to perform this glitch as non-host on patch 1.8.3. And ProfessorBroman stated such.