I wrote:

I currently have hydraulic surge brakes which have no lockout on the
actuator. The brakes (drum brakes) themselves have some sort of feature
that allow backing up. I'll try to find the make/model and give a pointer
later.

The coupler/actuator I have is a DICO (or Titan?) model 60 with a universal
coupler. I mention that only because it has no backup/lockout device on
the actuator and this is a hydraulic/mechanical actuator, not electric.

http://www.ne-ts.com/mac/bb/bb-306dico01.jpg

I believe the brakes themselves have what are called "freebacking shoes"
which is the feature I was trying to describe. I have no idea if these kind
of shoes can be installed into any system.