I'm hesitant to suggest this because someone will screw it up but...
Listen REAL CLOSE...
-pull the hand lever down
just a little bit,
After you pull on property and you are driving real slow looking for a parking spot simply:
-this engage the trailer brakes just enough to heat them up and dry them off.
-perhaps you could "feather" the hand lever, just a little bit, so that it alternately engages and releases the trailer brakes.
-I did this for a CPU trailer that I had to spot in the late evening, after all the employees had left...I never had froze up brakes.