I got a cheap $10.50 GWS speed control from Tower for a speed 300. It's tiny and weighs nothing. There are tons to choose from and all cheap. You'll want to cut or pull the red wire in the ESC receiver plug to disable the BEC.

On my JR 9303, I set up to use twin throttles and hook the speed control to the second throttle channel. In the 9303, you can set up two different throttle curves for each throttle channel. So for the turbine channel, I have both curves the same. For the smoke channel, the first curve is off, all points 0%, and the second is set up to run from around 40% at idle to 60% at max. The setting will vary by number of battery cells, type of pump and nozzles. In the throttle curve menu, you can select a switch to choose between the curves. So the Mix switch is the smoke switch on my system.

Using this method, you can set the smoke density to suit across the entire throttle range.