To unlock 'Comboing My Way Through' is fairly simple, you just have to beat 10 enemies in a row without taking any damage.
This can be done on any difficulty, but is obviously easier on 'beginner'.
The only real tips are, use focus if there are lots of enemies followed by executions, and don't panic. When an enemy is going to attack you, just deflect his attack, and then launch your own attacks.
With proper use of the deflect, you should be able to do this very easily.