Saying you spent 4 month preparating for the interviews is probably the worst thing you can do. In the eyes of the interviewers, ideal candidate does not prepare at all, or very little.
It is much better to say you were traveling or studying anything (renewable energy, precise agriculture, banking) or helping startups, freelancing on some projects etc.
Bear in mind that MBB interviewers are flooded by candidates whose only target is consulting and have no special focus. They however much more like candidates who shows a passion for some industry.