If you're going to try to experiment with a wild (or feral) yeast strain, I'd suggest that you do it with a small starter volume first. That way you can not feel too bad about tossing it if the fermentation begins to display undesirable characteristics. When I did my "Wild Thing" ferment a few years back, I pulled a couple of leaves and berries off of a mountain currant bush out on the property, and placed them in a jar with a mixture of honey and water at a starting gravity of around 1.050, if memory serves. Not a huge amount at first - maybe just about a half liter or so. Then, once i was sure that I liked the way the ferment was proceeding in the jar, I doubled the volume, added some Fermaid-K, and let that go for a couple of days more. Finally I was ready for the main batch - and I pitched that wild starter into my main batch of must.
It worked well - but as Oskaar points out, I've been making mead and dumping the lees onto the property here for quite a while, so I may simply have cultured a "feral" strain of winemaking yeast. It could have just as easily ended up being undrinkable swill, so the initial starter culture did two things for me - it helped to develop the colony cell count of the strain, and it allowed me to get a warm feeling early in the process that I wasn't pitching a strain known for generating lots of acetic acid, or worse....
A yeast exchange program of sorts.
