This question would really be better placed in the Lambic/Wild forum.
I have limited experience in sours, but from what I gather: Barnyardiness comes from Brett. If you want tartness (like what you get from a Berlinerweiss), you want to focus on Lacto/Pedio.
As for timing, the tartness can come on quickly or slowly; either way, it will develop over the course of months and years. Sour and funky beers are an investment, and not for the impatient. Plan on a year minimum.
For reference, Wild Ales and the Mad Fermentationist blog are both indispensable for embracing the funk.