I also forgot, buildin a bunch of flame turrets in front of the bunkers also helps wipe out a lot of the zerg. But like i said earlier, lifitng the buildings up at the end and throwing them out is a great way to buy lots of time.
I did this on brutal with usin the artifact only once. I took out the nydus. I had the 2 spots on each side filled wiht around 5 bunkers makin sorta a box witha bunch of scv's in side repairing and a lot of marines and some medics to shoot the stuff dead. there were siege tanks around also to help with that. The marines would pretty much take care of kerrigan before too much trouble happened. I had a banshee force for taking out the nydus worms. I ended up building a bunch of missle turrets just to help get the 1 use on artifact achievement. At like the last 8% or so i lifted all my buildings and threw them out, when they were far enough out kerrigan and most of the zerg just attacked the buildings and it bought so much time.