If there is a concern of water freezing when dumping it out over the
rudder, flaps or ailerons, then consider this.

The CRJ-200 has a limitation during certain icing parameters to move
the ailerons (wiggle them) every 5,000 feet during climbout. There's
been a few CRJ's that had the ailerons freeze up due to ice.

Seems like if we were to dump ballast, then during the dumping move
the control surfaces back and forth that are going to get wet until
the water is all dumped out.