Streaming replication: rsync to switchover

Hi,

I've setup streaming replication + file-based log-shipping, with a
hot-standby.

Everything's good, except I don't know which is the correct way to sync
the once-master db with the newly promoted master after a switchover,

1) I shutdown the master and touch the trigger_file on the slave. Now
the slave becomes the master.
2) On the old-master I create recovery.conf + archive directory for
file-based log-shipping.
3) I hope I can setup the old-master with a simple rsync, because the
operation could be really fast, being M and S almost identical, but I'm
not sure about the correct way to rsync them:

a) should I rsync --delete?
b) should I delete the pg_xlog of the old master, before rsyncing? (I'm
wondering what could happen if some of them never made its way to the
slave, that now has become new-master)
c) am I missing something? For example, I've read somewhere that one
should copy pg_control and pg_stat from the old slave to the new slave
but it doesn't make sense to me.

thanks for any hint,

--
rudi pettazzi