The 'Printer Friendly' version of the core rules can be downloaded from HERE.
The rules for this particular faction can be downloaded from HERE.
There is a starter set available for this faction composed by five Mutard miniatures.
All were fairly simple to assemble with the exception of the Mutard with the extra limb who has a couple of quite fiddly tiny 'hooks' on the stump of one arm which I have a feeling I'm going to be gluing back on quite regularly, lol.
This imposing fellow comes on a 40mm base rather than a 25mm one...
Mongrelmorphs - Assembled
If you happen to have missed them you can find the other articles at the links below.
Introduction to Punkapocalyptic
Faction - Black Blood Children (Part One)
Faction - Black Blood Children (Part Two)
Faction - Gangers
Faction - Junkers