Cash for keys is the only foolproof method with current moratorium.
We used that as a tactic at the FDIC during the bank crisis. It gave the borrower a financial incentive to leave without trashing the place.
Proved to be a cheaper, quicker way of resolving the issue without having to use attorneys.
FDIC had a lot of inventory, considering we closed down nearly 500 banks from 2009-2012.