If you want to boost this:
Step 1Go to your Kombat Card and equip a Backround / Icon and Border that gives the most FXP (Faction XP). Preferably focus on FXP per win or FXP per Brutality, obviously the higher the better. While you grind, check every now and then for new and higher modifiers for your Kombat Card that you unlock on the way (new backround for every 5 Faction Levels).
For Icon I suggest Hanzo (hit every QTE in Story Mode with Scorpion)
For Border you will get one with your favourite fighter after 25 and 50 wins.
Step 2Create a Kustom Game with a second Controller, pick
Brutal Kombat for instant Brutalities and if you want
Rapid Combat for even faster movement (spares some seconds - thanks to Dr. Lipschitz for pointing that out!).
Choose your favourite Fighter with an easy Brutality and start fighting. If you choose Kenshi for example, you just need to do 1 Throw and the Brutality will kick off.
1 second per match + loading time for rematch and an average of 600-800FXP per fight.
Here is a list with all Brutalities, what you need to do to pull them off and where to find them in the Krypt by IGN to pick your favourite one
http://uk.ign.com/wikis/mortal-kombat-x/Brutalities?objectid...As a last info:Be aware that you loose all (!!!) Progress in a faction if you decide to switch to another. If you switch, all XP is gone forever, every Faction specific Backround will be gone and if you switch before lvl50 you will have to start over again.
#Edit 04.05.15:Markyshizzle has made an awesome Video on YouTube, explaining every step of this solution. So if you want something more visual to understand how this works click here: