D3 Quick Start Guide: How do I keep my characters in sync? discusses the issue and gives suggestions. You may have already read it..
The idea behind the Video FX method is that you turn on the Repeater pass-thru option, and this allows you to have a little interactive game window embedded somewhere in your main window, for you to click in to move your other character(s) to you. You can line up a few little views of your other windows so that you don't need to move the mouse very far to accomplish this (reducing the amount of time you would spend clicking the
right spot -- not the
same spot -- in each window).
The simplest method to get 2 characters together is going to be to just turn off repeater, move to your other guy, and turn it on again. You can do this seamlessly while holding the mouse button down.
You can easily set up a button that turns off broadcasting while you hold it down in order to do this, using the Mapped Key Wizard:
So, (1) in the Wizards menu select Mapped Key Wizard, (2) select a Key Map (noting that the "Always On" Key Map is not toggled by the standard Key Maps toggle, so this Hotkey would be permanently active and potentially interfere with typing, etc...), and (3) pick the "Broadcasting Toggler" type of key to set up. (4) Give it a Name and a Hotkey, set it to toggle when the Hotkey is "pressed OR released" (so that it will toggle when you press, and toggle when you release as well). The default "broadcasting options" are probably sufficient. Once it's made, this Hotkey will be exactly
backwards from what you want, since the wizard is just going to turn it ON when you press and OFF when you release. To fix that, (5) go under Key Maps in the top left pane and select the Key Map you put it in; then (6) in the bottom left pane, expand the Mapped Key you created (it'll be listed with the Name and Hotkey you gave) so that you see Steps, 1 and 2 underneath it. (7) Right click the bottom Step and select "Move Up" from the menu, and then it will turn OFF while you hold the Hotkey.
This way when you have broadcasting enabled, and are moving around together and not synced, you can hold this new Hotkey to stop your other character from continuing to move. Run straight through your other character and at just the right moment, let go of the hotkey.