Simple solution, just change the value of the smoke resistor. I've used this in TMCC upgrades, and I remove the 8 ohm resistor and change it for a 22 ohm resistor. This is the value for TMCC applications, I'd have to know more about your DCC output voltage/current to recommend a value for the resistor.
I buy my resistors on Digikey, you need to match the physical size of the resistor to the one in that unit. You need around 5-6 watts of power dissipation in the smoke unit to generate decent smoke, that's a number to keep in mind sizing the resistor.