Here is a video by MiRai, on how to set up IWT/CTM in IS Boxer.
http://www.dual-boxing.com/showthread.php?t=45676

Basically, you want Click to Move enabled on the melee members of your team.
You can toggle that with /console AutoInteract 1 and /console AutoInteract 0.
1 = on and 0 = off.

You could opt for two IWT keybindings within Warcraft.
One would be only your melee toons and one would be all of your toons.

You'd broadcast (or make a mapped key) with all of them receiving the IWT command, when you want everyone to loot a corpse in turn, or to take a quest from an NPC, etc...

You'd broadcast just the melee's IWT, when you want to move the melee toons into range with whatever you're killing.




The post you have linked is a tad more advanced, but its not that hard.

If you were to make a castsequence for your toons...
Or you were to use Mercurio's two-step macros... http://www.dual-boxing.com/forumdisplay.php?f=14

You would have a button that you would want to spam.
You would have IS Boxer also send your IWT keybind to the melee toons.
So the one button would execute your DPS and ensure your toons are also in melee range (the melee ones anyway).
You would do this as a two-step process in IS Boxer...
Either on Press or Release, meaning key down is the IWT and key up is the Castsequence.
Or as alternating, one press/release is IWT and the next is the Castsequence.

Either way, you get IWT built into your DPS.
You can go with a manual IWT key quite easily, you'd just be pressing it quite often.