Here is a small, simple and inexpensive device you can build if you want to use the Aux Functions of a DCC decoder to move something. It may be a door, a coupler or whatever. This device will give you a small movement (4-6 mm). The actuator should be used for momentary movements, like releasing couplers or activating doors. Or you can use it with intermitent power for a windscreen wiper. The resistor can get hot when activated for a long period of time.
If you connect the actuator to the motor output of a decoder (orange and gray), you get a nice little servo.