While kettle souring is a good method and has certain advantages, it is NOT the only method of fast souring.
The Berliner Weisse I'm drinking is delicious and in fact hasn't been boiled.
Any source or blend containing Lactobacillus plantarum is awesome for souring.
OYL-605, TYB Lacto Blend, Sour Weapon L, ECY32, GoodBelly liquid probiotic, Swansons probiotic, Renewlife Ultimate Flora probiotic, etc.
You can pitch Lacto before, at the same time, or after you pitch yeast.
Earlier Lacto pitch, higher cell count, and higher temperature will all help make it more sour.
L. plantarum works best above 70°F.
Do not use any hops before it is sour. You can dry hop if you want afterwards.
Cheers