If you're using IS Boxer, right click on Steps in the bottom left pane.
Add a step, until you have one per shaman (or toon you want to do something).

Then on Step 1, send the keybind to the first toon.
On Step 2, send the keybind to the second toon.

Right click on Actions.
Key Actions > Keystroke Action.
As a target, set the toon you want.
And use the keybind for their Set Focus macro.