you probly dont want to do hard/brickwall type hi-pass filtering on your bass end, EQ doesnt just remove frequencies, it also changes the harmonic resonance, which means your 35hz sub may shift to a completly diffrent frequency, which will in turn resonate diffrently up the harmonic octaves of your sound, doubling up your 12db hi-pass (not a brickwall type filter) can help, but you still get sum changes.
My suggestion, if you are having problems with low freq rumble or mud, would be to ensure that all your sounds are properly hi-passed higher up, 100-150hz, then use a pure Sine to generate your sub.
If you need more dramatic EQ, you can set the EQ to Notch rather than Bell, this will give you an -inf cut