How can I tell what kind of fan controller to use?
Could you post the picture of what's left of the fan, which you have dissected/sacrificed?  Does it have a built in controller or motor driver?  

If you have an oscilloscope - probe the lines.  You can also disconnect one line at a time and see how the fan and the host will react.  This could shed some light on the purpose of the lines.

Most fans have only 3 lines: motor+, ground, tach.  Without knowing anything else, here's an educated guess about the 3 remaining lines:

PROG is for factory use.  Perhaps, the fan has a built in memory (?) for calibration parameters (?).  

ENB is a logic level on/off signal.  Some times, it can be used for PWM speed control.

IDENT allows the host to identify the fan.  On the fan, it could be connected to one of the following: a resistor, which identifies the type of the fan a nonvolatile memory shorted to some other pin, which can tell the host whether the fan is connected at all or not