Do I need to set up the transfer with the FFL before the gun ships?

Also ask whether the seller already has that dealer's license on file. The big online sellers keep thousands of FFL licenses on hand, so sometimes you just give them the dealer's name and they match it automatically.

Call the FFL first. Most want to confirm they accept transfers, know it's coming, and send a copy of their license to the seller. Some have an online form for exactly this. If a gun shows up unannounced, a busy shop may sit on it or refuse it — a five-minute call saves the headache.