DDNS, BIND and leftover .jnl files

I've looked at this before.
Restarting named will flush updated data from .jnl files back to the zone file, but there's also another way..

rndc freeze <zone> but this will disable DDNS, so it should be followed with a rndc thaw <zone> to re-enable it, and should clear up the .jnl files.

There's apparently a rndc sync in Bind 9.9.

With bind 9.9, "rndc sync" is not enough; you also need the "-clean" flag:

sync [-clean] [zone [class [view]]]

Sync changes in the journal file for a dynamic zone to the master file. If the "-clean" option is specified, the journal file is also removed. If no zone is specified, then all zones are synced.