Good guide — Nunchuk is one of the best tools for this use case. A few things worth adding for anyone setting this up:
Before you fund the wallet
Test a full recovery before moving real bitcoin in. Create the wallet, export all four keystores (including the watch-only config), close and delete the wallet locally, then restore from scratch. This surfaces any issues with your backup process when the cost of discovering them is zero.
Key distribution matters as much as key count
3-of-4 with all four devices in one location is worse than 2-of-3 distributed geographically. For a business or partnership scenario, each signer should ideally hold their key on separate hardware in separate physical locations. Also consider: what happens if one signer is unavailable for months? Document a recovery procedure in writing before you need it.
Nunchuk-specific tip
The PSBT workflow in Nunchuk lets each co-signer verify transaction details independently before signing. Get everyone comfortable with inspecting PSBTs — outputs, amounts, change address — not just blindly signing. This is the whole point of multisig: each party independently confirms what they're approving.
The 4th key
In a 3-of-4 setup the 4th key is your safety net. Some people hold it with a lawyer, some keep it in a different country, some use a hardware wallet stored off-site. Think explicitly about who holds the 4th key and under what conditions it gets used — document that agreement between partners before funds go in.
Good guide — Nunchuk is one of the best tools for this use case. A few things worth adding for anyone setting this up:
Before you fund the wallet
Test a full recovery before moving real bitcoin in. Create the wallet, export all four keystores (including the watch-only config), close and delete the wallet locally, then restore from scratch. This surfaces any issues with your backup process when the cost of discovering them is zero.
Key distribution matters as much as key count
3-of-4 with all four devices in one location is worse than 2-of-3 distributed geographically. For a business or partnership scenario, each signer should ideally hold their key on separate hardware in separate physical locations. Also consider: what happens if one signer is unavailable for months? Document a recovery procedure in writing before you need it.
Nunchuk-specific tip
The PSBT workflow in Nunchuk lets each co-signer verify transaction details independently before signing. Get everyone comfortable with inspecting PSBTs — outputs, amounts, change address — not just blindly signing. This is the whole point of multisig: each party independently confirms what they're approving.
The 4th key
In a 3-of-4 setup the 4th key is your safety net. Some people hold it with a lawyer, some keep it in a different country, some use a hardware wallet stored off-site. Think explicitly about who holds the 4th key and under what conditions it gets used — document that agreement between partners before funds go in.