I just started this one myself, using cheats. First I did the level skip cheat (L Shift + L + End) on both Normal and Agent. Got all of the mints for finishing each level, plus Phantom, Ace, Legend, Blitzkrieg, and somehow Ninja glitch popped for me.
20 mins and I already have 300/1000 mints. All that's left now is to do all the kills + collectables, which I plan to do with the youtube guides and/or guides from places like gamefaqs. I have a feeling this wont take very long at all.