Public Passphrase & Sweepable Multisig

Sorry, what I meant when I said that it had been used before was that you’ve used it on both blockchain.info and coinb.in (unless I misnderstood).

Yes, unfortunately that is the case as far as I am aware. Check out the following couple of links and don’t hesitate to read through https://forums.counterparty.io/c/support/knowledge-base or make a thread in the support section if you need help setting that up.