The exemption for used guns not on the "not unsafe" list (
caag.state.ca.us/firearms/certlist.htm) does indeed apply only to person-to-person or consignment guns that were already in the state. There's no such thing as a private transfer, as all gun transfers in the PRK must go through an FFL, but an FFL cannot "stock" or import a non-listed gun. He *can* have it on consignment, and can do a person-to-person transfer, though. C&R pistols are fully exempt, so FFLs can import them and sell them just like a listed pistol.
Anyway, given that the SIG P228 is listed, you'd simply need to send the pistol to the buyer's PRK FFL, and the FFL will handle the transfer just like any other PRK pistol (BFSC/DD214 or other pistol exemption, NICS check, DROS, 4473, 10-day wait).
-Troy