Well, you can do it with Parameter Modulation, but I find that setting the ranges in a bit tricky. Have a look at the attached project.
Here I have ReaSynth and ReaVerbate on a track, with ReaControlMIDI acting as a controller.
-- in ReaControlMIDI, I selected a single channel, enabled Control Change and selected Cc25 and C25.
-- in ReaSynth, [Param] I selected Detune (the Tuning slider) and linked it to ReaControlMIDI's CC24
-- in ReaSynth, [Param] I selected Sustain and linked it to ReaControlMIDI's CC24 too
-- in ReaVerbate, [Param] I selected Wet (the Wet / Dry knob) and linked it to ReaControlMIDI's CC25
-- By trial and error, I set the Offset and Scale for each.
Now, changing the CC24 control changes Tuning and Sustain in ReaSynth. And changing the CC25 control changes the Dry/Wet mix in ReaVerbate,
But .. have a look at BlueCatAudio's atchWork, that might be easier / more flexible.
http://www.bluecataudio.com/Products/Product_PatchWork/
And for multi-track parameter modulation, have a look at
http://forum.cockos.com/showthread.php?t=86188