Eventually, we found the following glorious DocID on Metalink: 427577.1. Bookmark it now.
It identifies a few patches you'll need to install on GC in order for patching to work. Or you end up with some very irritating, strange, and mostly undocumented errors:
ERROR em.paf_jobs executePAFCommand.142 - Problems with the directive urn parameter format.There are others, not totally related:
oracle.sysman.emgc.provision.UrnException: The URN, 'null', is not properly formatted
There was an error saving 'p4898608_10.2.0.4_2000' below 'OracleSoftwareUpdates' in the deployment libraryFixed that one by deleting from Deployments>>Provisioning select and deleted p4898608.
There's a really handy guide to look at -- grid-automation-deployment-procedures.pdf Found that to be pretty useful.
Couple more random things:
1) Setup your software library: info here
2) Run the metalink & opatch update scripts. Now.
3) Patch the system from the docid above.
Should work. Hasn't for me yet, but when it does I'll post the last lil bits.