My Russian Pickle has a very robust tone control. Whether it comes before or after the fuzz is unknown to me...I just know it works.
Most of the muff variants I've tried impact the tone OF the fuzz, (or after the fuzz). I want to send a less-bright signal INTO a bright fuzz (if that makes sense). The tone knob on 99% of the fuzz pedal's I've tried don't achieve the desired effect since they're altering the sound of the fuzz itself, rather than the tone of the signal entering the fuzz.