There's no real shortcut. You just need to study the qbanks constantly. This is a good reminder that you should probably start studying the shelf before you go back to the clerkships.
a lot of people suggest getting the UWorld Q-bank for a 2-year subscription and basically start studying during the final year of their PhD. Works out perfectly if you take step 2 CK right at the end of MS3, which is ~10-12 months at most programs.