I think Duff is a very versatile bass player, his basslines are simple most of the time but very groovy, that's why he's my fav bass player. They do not follow the same pattern..
Anyway, from what I know, Duff uses the following equipment/set up. He usually uses a fender jazz special which is made in japan and more recently, he uses the fender aerodyne, which is also made in japan if i am not wrong. But his main bass is still the fender jazz special. For pickups, he uses Seymour Duncan hot stacks, the STKJ2B for the bridge. I am not sure what he uses for his neck pickups though. For amps, he uses Gallen Krueger. For effects wise, he uses the Yamaha SPX 90 for chorus and a MXR DI box. For strings, he uses Rotosound swing bass 66, .45 gauge. Hmm, that should be about it. The DI box plays a big part in getting the 'Duff' sound, seriously. Oh, I usually add more treble on the DI and less bass, but on the amp's eq, I add more bass and less treble to balance out. That's my preference
Just play around and you can pretty much get it. I got more of his live sound rather than his studio sound. They sound a little different. I have yet to get a chorus pedal, not the yamaha one though. Prob a Boss.
I hope this helps. I am no duff sound engineer. Lol. Cheers!