The filter takes some getting used to. The main thing to understand is that it is not like your average active treble control.
To put the filter in neutral, turn the knob all the way open. As you turn back the knob, you're lowering the cut-off frequency. This means you're filtering out the frequencies above that.
The Q switch adds a boost at this cut-off frequency - flip it down, hit a note and then quickly turn the filter pot all the way down, and all the way up again. You will hear a wah-like sound as you turn the filter pot either way. When engaged, the Q effect can be heard at the start of the note. On a sustained note, switching the Q on and off has little or no effect.
Personally, I always leave the filter on my Spoiler wide open. I have a three-position Q switch that offers 3 and 6 dB boost options, which is softer than the standard 8 dB (a little harsh to my ears).
The treble and bass boost/neutral/cut switches should work as normal.