I Sous-Vide my sour mash Berliner beers. Since the grain bill is not large due to the low gravity I does not take up significant volume. I add grain and strike water as I would to my mash tun only I add it to a bag. I mash for an out in the bag and then throw in ice water to bring the mash temp down to 110 degrees. At that point I toss in some raw unmilled 2 row and vacuum seal the bag. I place it in a water bath held at 110 degrees for two or three days. I pull it out hang the bag in the kettle and poke holes in the bag to drain or if I am in a hurry I strain off the liquid and start my boil. From there it is just like any other beer.
Trick to sour mashing and using lacto is keeping oxygen out of the mash for the extended mash time. If you let O2 in there things can go nasty on you pretty fast. Vacuum sealed in a bag eliminates that issue rather easily.