I would say the best thing is time. Brett can ferment clean, but then after time it will consume most everything else in the beer. You could mash higher and sparge hotter in hopes of giving it more food to chew on.
I've done 100% brett B and L beers and the B was like licking a horse (not that I've really ever done that.)
The Crooked Stave yeast i used from an older bottle of petit sour was phenomenal in every aspect. One of my favorite yeasts.
One way I have found to get (too much) funk is to underpitch the brett. Its probably not the flavors you desire, but it does produce some wacky stuff. You could split a batch and blend it in... that's what I plan on doing this summer with my insane-0 horse keg.
I also made high IBU worts and pitched ECY 01,03,04, my house strain, WLP655, Jester King starter and found that there was less funk in those (so far), I'm guessing in part due to the higher bitterness in the beer. Time will tell though. I plan on dry hopping the tar out of them and seeing if a "Sour IPA" will blossom.