The battery discharger is a good idea. The hard part is to discharge them down to the optimal voltage (.9~1v per cell). A lot of the better chargers have this as a function. I am in industrial automation, so before I bought one that did it, I programmed a PLC to do it across a power resistor. I monitor the voltage at the pack using an analog input and shut off the relay when it is complete.
You can shunt them across a 12v turn signal light bulb, but you need to shut off the discharge before at the right time so the cells don't reverse and kill the pack.

I hope this helps. Maybe one of the folks here will post a link to the battery clinic and it will explain more. A lot of people do not purposely discharge them and have had good luck.
Curtis