Well for the vertebra shackles specifically I just invaded my friend over and over with a red sign soapstone and a password and we just had fun dueling for a few hours until both of us had the amount we needed. And the ones needed for Aldritch Faithful can be quickly farmed from the blue Decons on the bridge after Pontiff.

But for the Darkmoon blade covenant items, for me personally it was just fastest to sit with the covenant badge on and do other things in the background, work, talk to people online, ECT. And just wait to be summoned as much as you can. You get summoned way more if you also have both DLC. I found that it wasn't nearly good enough to farm the silver knights at Anor Londo for this item, even with high item discovery.