My second setup (first was alt-tabbing) included downloading keyclone as you need a key replicating software to all screens, although there are free alternatives, search the forums.

So 1 screen was master, 2nd was slave, i blacklisted all movement keys in keyclone so they wouldn't pass to 2nd screen.

Macros I used were:
Toon 1
Key bind 1
/cast firebolt

Toon 2
Key bind 1
/assist toon1
/cast firebolt

or

/target toon1
/cast heal

That was pretty much it. i did have a /follow toon1 macro for keybind ` (left of 1)

Then I discovered 5 boxing,innerspace and my brain melted...