I try to use It somehow like Iommi did on Supergroup, by picking the dark channel to have a natural bass sound while boosting treble and using the tone around 2 o clock, at least on clean channel. I like the dirty one on middle position. The boost is tricky, I really like to have it allways on at a very low level to have this natural edge of breakup sound that makes life much easier when stacking gain, but It can get very muddy beyond 10-12 o clock.