After two days of stirring I've had fermentation begin in one of my buckets without repitching.
This bucket contained 6 gal unpasteurized apple cider, 3 lbs dextrose, 1 tsp potassium metabisulfite, and one swollen activator pack of Wyeast 4766 Cider yeast. I pitched the yeast only ten hours after dumping the potassium metabisulfite, so now I can personally attest to the hardiness of this yeast strain.
The other bucket contains 6 gal of cider, 1 tsp potassium metabisulfite, 2 lbs dextrose, and a packet of Montrachet yeast by Red Star. There are no signs of fermentation taking place. I'm fairly certain I'm going to have to make a strong starter and pitch that after another day or two of stirring. Any suggestions with this one?
Lastly, I've got 3.5 gallons of cider in a glass carboy with Wyeast sweet mead yeast and .5 tsp potassium metabisulfite. This one has not started, though I achieved success with the other Wyeast strain. I'll probably have to repitch this as well in a day or two.