I get the idea that they can help lower the louds and raise the softs. I don't get how to use them - what knobs to twist to do what. Same for other similar type filters/boxes with "sustain", "attack" and "release" - like enevelope filters. I've read that you can help enhance/increase the Tele "twang" by using a compressor. How? What knobs do you twist to do that? I don't get what "attack" and/or "release" does to tone.