Not that I'm planning to do this anytime soon, but I'm interested in the process itself. The micro near where I live (Microbrasserie Charlevoix, their website is atrocious, don't bother searching for it) has a series of Belgian beers that are pretty damn tasty, especially the "Blanche", wich is probably a simple wit. They don't exactly brew to style, but you can taste the wheat and pils.
It's my gf favourite craft brew: slight clove, cinnamon and banana (no taste, only aroma), intense spice feeling and moderate malt. Altough I haven't been able to talk directly to the owner, the small amount of research I have done (ie. sampling) shows that they use the same yeast for all their Belgian style beers and altough it might not be exclusive, I cannot find a direct match.
So I tought about buying 3 500ml bottles of the 5% ABV "Blanche" and cultivating the dregs from them. I really don't know what will come out of this, but it'll be a fun experiment ! Can I just sanitize the lip with a flame, pitch the sediment from the three bottles into a masson jar with 150ml of 1.030 wort, wait until fermentation finishes and then step up to a liter of wort, or do I need to carefully step up ? Do I need to keep everything in the fridge ? Getting fresh bottles is probably crucial, but I live 2 minutes way from 6 places that sell the beer, so it won't be a problem.