I understand what you are going through - as a former experienced hire myself, I did find it much harder to prep without my school's resources. There are ways however. Warning, obvious conflicts of interest here but...
1. If you aren't sure what exactly what you are looking for / "what good looks like", you have dozens of current/former consultants here who specialize in helping you how to figure it out. It won't be free, but I'd argue that getting into MBB is well worth it
2. Once you know what you are striving for, then practice cases with fellow applicants make sense
3. You probably have met MBB consultants in the past, perhaps in a personal setting. Don't hesitate to reach out to them for help - worse they can say is no.
I really cannot speak strongly enough against Case In Point's framework/case chapters - please don't waste your time on it. You can also look up Victor Cheng's 6 hours of free video on YouTube, well worth anyone's time.
When there is a will, there's a way. Good luck
