No. Do not use the frame for any electrical connection except the
left track feed to the input of the decoder. The decoder wires must be
your sole source of on board power for lights etc.
Usually the blue output wire of the decoder is common PLUS.
You will have to check the decoder manual for the color wire
that is a decoder switched negative output for lights, etc.
Be sure to check the decoder manual to determine if the
smoke unit goes through it. It may draw too much current.
One experienced with the smoke unit could tell you if it
can be connected across the raw DCC track current. jIf it
can be, you would use the frame for the left track current
and the red wire from the right track wheels.