Assuming the smoke unit runs directly off track power,insert a diode in series to one lead of the smoke unit and or the light bulbs. That will effectively cut voltage in half. In command the unit will get effectively 9 volts.You can use 2 , 1n4001 didoes in parallel or 1, 3 amp diode. You can get these at Radio Shack or in quantity from an electronics supply house..
Dropping voltage with diodes is explained here
http://www.jcstudiosinc.com/Bl...3&categoryId=426
You may also wish to convert your caboose to LED lighting shown here
http://www.jcstudiosinc.com/Bl...7&categoryId=426
Dale H