I've brewed 2 berlinner weiss' over the years and have used a normal mash schedule, with a protein rest. Add Wyeast 1007 (got the strain from Wyeast, their recommendation) and the Lactobacillus (I've also used Pediococcus) to the primary and let it go. It will end up with a nice level of sourness. I bottle my bw's and let them age for about 6 months prior to sampling. I've heard that the longer you age them, the higher the level of sourness. However, for my first one, I let it go in the bottle for about 1 year and the level of sourness actually decreased. I vote to drink it up in about 4 months time after sampling.