Barrel Conditioning

Finally got some time to start assembling my Filastruder and I noticed that the inside surface of the barrel has rust and other contaminants.  Is there a need to clean the inside surface of the barrel with something like a stainless steel wire pipe brush?  I don't want to end up doing something I shouldn't by trying to get the inside surface clean and smooth. 

Or is the proper method simply purging out the barrel with the supplied pound of ABS as the correct first step before extruding filament for use?