I used to do it with ReaEQ and PM but I was told that modulating an EQ in this way could introduce audible phase distortion due to the PM updates happening once per audio buffer, so the changes are stepped. Thinking about it now, it might not be a real issue. Surely any decent EQ plugin would implement internal parameter smoothing anyway?
Anyway around the time I was worrying about this, TB FlX was released and it was so easy and affordable that I bought it and never looked back.
edit: I was convinced I could hear the phase distortion with ReaEQ + PM but perhaps I was fooling myself. Need to design a test.
