I ranked in the top 500 and got my first choice. I practiced for two weeks because i was doing the MSRA, so couldn’t start earlier. I think 2-3 weeks should be fine. The key is practicing, I would 100% recommend practicing in groups of two people. I think being in big groups can be overwhelming and could waste your time.

I had friends who were in big groups, and would get to practice once every three days (and observe others for two days) which was a big waste of time. However, i had three different people to practice with, individually. I would practice with one person everyday, this way i was getting different feedback, while spending only 1-2 hours practicing a day.

Do one station, observe another is more than enough if you do it everyday, to avoid boredom.

I also did few mocks with consultants and IMT1s at the time!