First off, I have absolutely no experience with Reason.
Within DAWs just about any knob/slider/whatever that can be manipulated through a MIDI controller, will be documented. Check your documentation which CC number it will be and then check the controller on how to program the knob/slider/etc. of your choice.
I know it is not a direct answer, but it will help when you want to remotely manipulate some other filter of a synth to know how to find the needed data.