Overlay or Screen Segmentation where click is broadcast

Hi all, returning multiboxer here. Used to multibox WoW about a decade ago and I'm giving it a try again. One thing I'm struggling with is remembering how I went about setting up my healing last time. I recall I used an addon called grid and I would play from my main character and be able to click on people in my raid/party and clicking that particular section of my screen would be broadcast to my healer character who would actually perform the action.

I think it may have been a snapshot/copy of my healer's screen that was overlayed onto my tank's screen but I'm unsure. Anyone got any idea what I'm talking about and could point me in the right direction?

[lax]

MiRai's Healing 101 video will refresh your memory: https://www.youtube.com/watch?v=6qHo0FTuGV0

This video and more info here: http://isboxer.com/wiki/Video_FX

Awesome, thank you.