Souring Wort:
As an example, say that 5 gallons of wort has a pH of 5.0 just before pitching the Lactobacillus culture. Begin by adding 5 mL (1 US teaspoon) of food grade lactic acid to the wort for a target of ~4.4 pH. Stir gently, then take another pH reading. Continue to add 1-2 mL of lactic acid until the wort has the desired pH. Once a pH of 4.0 - 4.4 is reached, pitch the Lactobacillus culture. This small amount of lactic acid shouldn't have much of an impact on flavor.
OYL-605

Steps

1-2 days before brewing make a 1 liter starter of 1.040 wort, and add your vial of WLP644. Let it sit at room temperature until use. Also make 1 liter of 1.040 wort, and pour OYL-605 into the starter. Incubate 24-48 hours at room temperature to increase the cell count.

Mash in at 145°f for 60 minutes; if hops have to be used, then make sure to add the hops to the mash.
Sparge as normal.

Bring the wort to a boil and then turn the heat off (no need to boil for more than a couple of minutes).

Adjust PH ~4.2 to limit growth Clostridium butyricum and other potential off-flavor bacteria. Not necessary, but this is a best practice suggestion.

Chill the wort down to 95°f, and transfer to a CO2 purged carboy or keg. Add the 1 liter of OYL-605 Lactobacillus Blend starter. Allow it to sour for 24 hours. No external heating is required.

After the souring phase, chill the soured wort down to ~70°F and pitch WLP644 Trois (boiling to kill the Lactobacillus before adding the WLP644 Trois is optional; see kettle souring). You can aerate if you feel necessary. After 2 weeks a stable gravity should be reached.

Rack or transfer off as normal to bottles or a keg.