Goblins and gnomes can tame the Iron Juggernaut hunter pet without anything special, but other races need to use the Mecha-Bond Imprint Matrix which is created by engineers.
Most of the raid can be soloed at max level, except for Galakras which needs another player. So you need a friend, but preferable not a hunter, since the crafting items only will drop once, so only one person can get them. The parts drop in any difficulty, so if you play with another hunter, you can do both normal and heroic mode to make sure both of you get it. However, each player can only get one set of mats each week!
How to get the parts for creating the Iron Juggernaut
Start the raid by killing Immerseus, the Protectors, Norushen, Sha of Pride, and then Galakras. Head to Iron Juggernaut and loot Pile of Juggernaut Parts. Now kill the Dark Shaman and head towards the underground area. Here you will find the Green Color Bucket in the southwestern hut. After looting this kill General Nazgrim, and go to kill Malkorok. The Green Paint Bucket is in the Wolf Den right part him.
Now head to Siegecrafter Blackfuse. Siegecrafter Blackfuse will drop Blackfuse's Power Core, which is the very last item you need in order to craft your first Iron Juggernaut!
If you want the teal or grey color, keep going. The teal color bucket is found in the western corner of the Spoils of Pandria encounter. If you want the grey one, keep clearing the instance, and look for the grey paint bucket in the stack of crates in the tunnel between Paragons of the Klaxxi and Garrosh's room.
Tame the Iron JuggernautSo now you have all the parts to create the Iron Juggernaut, and you craft it by right-clicking on the paint bucket you wish to use. This will create a Deactivated (Color) Juggernaut, and this can be summoned by another right-click.
The Iron Juggernatur will be neutral, and other hunters can probably steal-tame it, so you might want to be somewhere safe like inside an instance or in your garrison. It's really easy to tame, but you should use Aspect of the Turtle to be completely sure that you tame it.
The items are of course consumed on use, so if you want another color you need to do one more run in SoO next week. Since you can get all the paint bucket in a single run the next one should be shorter, since you don't need to clear anything after Siegecrafter Blackfuse this time.
Please use the comment section if you got any questions about the Iron Juggernauts!