If you want less of a flavor impact from the brett here are two suggestions
1. Wait till primary fermentation has fully completed with your abbey yeast. The less residual sugars (lower FG) means that there will be less for the brett to consume and change your flavor profile. More residual sugars (adding brett before fully reaching FG) will lead to more brett flavor as they consume the sugars.
2. After primary with your abbey yeast, rack the beer to a designated keg and pitch your brett into this. Allow to age in cool temps (58-60) if possible. Be sure to purge your keg with CO2 and flush the headspace as well. I have found this provide the best flavor development for brett beers without them running away with the beer (overly horsey, goaty, farmyard, etc). The other plus is you can sample from the keg easily and when the flavor is just right, cold crash, carbonate and drink up!
