White Labs manufactures all of our Yeast Bay cultures as well and they do not concentrate their Brett unfortunately, so for primary a starter is needed. Not a huge deal ultimately, I always recommend a starter for Brett beers anyway as pitching a starter at peak activity DRASTICALLY cuts down on lag time and overall fermentation time.
For a Brett starter, simply make the same starter you would for Sacch, but you'll need to let it ride 72-96 hours more than likely to get it to peak activity, running it around 75-78 F will also help get them active faster.
Good luck! Fell free to reach out directly to me at [email protected] if you have other questions, I tend to get to emails pretty fast. Always happy to provide info to support the use of White Labs and Yeast Bay cultures!