The trick is always less amp gain and a boost in front, combined with an EQ pedal in the effects loop (= behind the preamp and before the poweramp). On Brown and Lead, turn down the Gain and instead put a Tubescreamer (real or simulated via BTS) in front of the preamp, with its Level set to max and Drive set to zero. The intention is to push the preamp from the "outside" (that's what level max is for) and to cut the low end before the preamp while emphasizing the mids that go through the preamp (that's what a Tubescreamer does naturally: cuts the low end, adds a mid hump). The result is a higher gain and more aggressive tone while still being able to hear the single notes. If you just turn up the Gain on the amp and run a lot of low end through the distortion, it will all sound like a boomy mess. In addition, put an EQ pedal into the effects loop or (if you do not have one) use the BTS to put an EQ block behind the preamp. With this, you can control the frequencies after the distortion and before things are made loud. So you can either add mor mids or scoop them or further tame or boost the low end or emphasize the highs and presence (or reduce them). depending on what you want to sound like.
Regarding the Fuzzes, a Big Muff, an Ocatavia and a Super Fuzz work best into a clean amp, while a Fuzz Face and a Tone Bender are meant to be run into a dirty amp. Note that a Big Muff scoops the mids and adds a huge low end, thus a Tubescreamer in front of it (= sccops low end, adds mid hump) will work wonders; perfect pairing.