My example had more than just brett b, but...
Did a baltic porter(kind of I guess) with all brett (multiple strains, but there was brux in it). Primary fermentation was around 66 for 3 weeks (gravity got down to 1.013). Then it went in the fridge at 52F for about 2 months. Gravity crept down to 1.009 and stopped.
It's a powerful critter in my experience and it should get the job done.
I'm in the planning stages of a sour lager now... I'll be interested in your results with just brett b.