building a starter from dregs

@OldSock has written about it here, and probably much more extensively in his book, American Sour Beers. I think basically a low-gravity starter, with maybe some yeast nutrient, is all you need, but then you have to figure out what you're going to do with the bugs. I don't have any experience with this, and I don't know how many steps you should use to ramp it up to pitching numbers (if that is your goal). Here are @OldSock's thoughts on maintaining cultures.

 

1.010 to 1.020 wort, roughly 10-50ml with nutreint. I use lab vials, you can do it in a small mason jar. Shake it up every so often, couple times a day, and then crack the lid to let any CO2 escape. After about 2 weeks of this, pitch it all into a 1.020 100ml starter. Then after another week or two step it up to whatever size you need to ferment with.

 

I wouldn't worry about decanting the spent starter until you are ready to pitch into your batch. I wouldn't sit on it for too long before pitching. The longer it sits the more viability you lose. You could do another starter just before you're ready to pitch, but the more steps you take the more you build up bacteria over yeast (they reproduce faster and raid all the simpler sugars). I would go 10ml 1.010 -> 100ml 1.020 -> 1000ml 1.040. 2 weeks for each step. After the last steps 2 weeks crash for a week or so to get all the cells out of suspension, then decant and pitch.

Crooked Stave should give you enough Brett for primary after those steps. Maybe pitch it with some Brett B Trios.