Electrical block detection works by detecting a current drawn from the track. It is very effective at detecting DCC decoders in locomotives, even when the motor is not running. however, computer based control works best when the whole train is detected. Most wagons and carriages do not draw any current, simply because they put no load on the track.
A simple solution is to create a resistor wheelset, and have several along the length of the train. Simply put, a resistor wheelset is an axle that has an electrical load attached. A 10KΩ resistor is ideal. The challenges are to put it there, and to connect it. This page tells you how!