You can pitch the yeast and and lacto at the same time, or not. Doesn't matter. Either way, the lacto will just hang out in the background until the yeast are out of the way. Lacto (and other brewing bugs) are slow eaters in a secondary carboy, so I'd plan on a 3-12 month souring time. How long to give it depends on how sour you want it. Sample it once a month, that'll be your guide. You don't necessarily need a second set of equipment to deal with sour beers provided you clean and sanitize very well.