There is an article in one of the last 3 issues of Zymurgy about doing all brett beers, and there are 3 recipes. If you are posting on here, do you have a subscription? You can get the e-issues if so.
Interested in this thread as I'd like to do an all-brett farmhouse.
My copy of that issue is at work, so I can check it tomorrow, but I believe as one poster said, if it is ALL brett (no pedio/other bug), you will have more dryness/acidity, less barnyard.