I am trying to both light and get current to couplers for the crew car that comes with the 4MFOR 47951 set. I have installed the light kit (73150) and am not sure which coupler set to get or how to install them. The two options seem to be 72020 and 72021. The 72021 looks like a better option, but looking at the downloadable instructions it is not clear how to get current to the one coupler or bridge to the other coupler. I assume through the lighting kit. The pictograms in the instructions are not that great especially at the wiring. I have the springs already installed under the contact strip and need to buy a couple conducting couplers, but I also need the items and instructions for wiring with a light kit installed.

If you are going to put lights only in the begleitwagen (Accompanying coach), you will only need to install the lights and the slider on that coach.
If you want to source the power from the locomotive of the train, you will need to install the contact and the current conducting coupler on at least one end of the coach as well as the current conducting coupler and a contact/wire to the corresponding lead or slider on the locomotive.

I would simply install a slider on the begleitwagen, as this way it could operate at either the front or the tail of the train and you could operate the lights when the train was not connected to a locomotive.

Regards

Mike C