eff all that...just brew a batch, cool to about 100 or so and pitch a built up starter of dregs from one of your favorite commerical sours...way less complicated.
Of course, I've also used the homemade lacto starter method...but combined a cup of crushed grain and 100 degree sanitized water in a mason jar and kept at high temps (80-100) for about 1.5 weeks...then pitched into a 3 gallon batch...let that get nice and sour for about 8 months, then blended back with 3 gallons of a 2 month old version of the same beer.
never used sour mashing though...
Primary: Sour Brown, RIP Stout
Kegged: Pumpkin Stout
Future Brews: a gluten-free beer for my mother-in-law, barleywine