chainlube,
It is simple and it is just as you said. An unlicensed person ships the firearm to the buyers FFL, to the address on the buyers FFL copy. You really don't even need the signed FFL copy, you just have to be sure that the addess you are shipping to is actually an FFL. But you don't want to be hanging in the wind if some question arises so the best way to cover your butt as the non-licensee shipper is to have a signed copy of the FFL in your possesion before you ship.
FFL to FFL is not needed and people and/or sites suggesting that it is the law, are wrong.
There are requirements for the non-licensee to use a common carrier (UPS, FedEX) to ship CERTAIN firearms, but if you always use a common carrier you will always be within the law. The post office is not a common carrier.
Dig around in the FAQ on the ATF's website and they answer the exact question there.