I believe that Farson and Flagg are actually the same. I have read the graphic series. I think Flagg used his dark magic to create a decoy who was under his control to act and talk as if they were Farson. In the books we never actually see an encounter with The Good Man, and in the comics (as I recall, could be wrong) we never see his face (The Man With No Face...). Plus at the end of the comics, it says that the man behind it all is Walter, indicating that he is the true mastermind.
I think any time Flagg and Farson are together is simple trickery of the wizard. Flagg is Farson.