I’ve done about a dozen single gallons with wild yeast and two keg batches. A few have come out exceptionally good and quite a few also that were crappy. The difference boils down mostly to two factors:
1) Keep handling of the juice to the absolute minimum. If you press the juice yourself, cut off any rotten spots or bruises on the apples. If you go to a press, make sure that they steam clean it between pressings. On pressing day, show up as early in the day at the press as possible, so the juice hasn’t been sitting in the holding tank for any length of time. From the holding tank, pour it straight to a sanitized carboy with a sanitized bung and when you get it home, put a sanitized airlock on it. Any time you check gravity, be super careful with sanitation.
2) Don’t let the FG get below 1.010. Actually, the lowest I’ve been able to get a batch to go and still taste decent is 1.014, but you might be able to do a little better. My experience with going below 1.014 is that the juice would either pick up weird flavors or lose flavor.
The juice will have enough yeast to spontaneously ferment. It may take several days. For one of my better batches it took a week for fermentation to start, so don’t give up before at least a week.
If you are successful in a wild yeast batch, then you will have achieve good enough sanitation so that you don’t need to add k-meta before you add yeast. The cultured yeast will always dominate the wild yeast, so you have the cultured yeast taste, but also a little flavor from the wild yeast. Plus you don’t have to wait for months for the k-meta sourness to wear off.