Mid tier accounting firm M&A interview

Yes yes, spare me the nonsense, its not Goldmans or anywhere near, but not all of us are harvard grads, and even more so, won't be given a chance. So I have this opportunity and I am still happy about it.

I have a final interview with 2 of the partners, any idea on what sort of preperation I should undertake for it?

Also, anyone with info on working for a midtier accounting firm on M&A would be interested to hear what its like. Transaction sized im told are generally in the $10m to $100m