If SWIG failed for you, my confidence level in your likely success with interrogate is not high. SWIG is designed to be user-friendly and to work with a wide variety of code. Interrogate, on the other hand, is primarily designed to work only with the code within Panda itself. It has occasionally been used with limited success to directly expose third-party libraries (TinyXML), but usually it is used to expose Panda wrappers around third-party libraries (ODE).
Searching for 'interrogate' within the makepanda source should give you plenty of examples.