For anyone still following this thread, making a lacto-only starter is the key to this style. I made a 1 liter starter and kept it near 100 degrees with a heating pad and let it go for 2 days on the stir plate. The finished product has the crisp and lively twang that is the hallmark of this style. You can't beat the cost of less than $2 a gallon either. Love me some Berliner Weisse!
Thanks for the update Dee.
I brewed my Berliner Weiss this weekend. It's a no boil which I batch sparged with water at 70F. Efficiency was 80% confirming the suspicions of some that cool water would not effect the efficiency of batch sparging significantly. I pitched the lactobacillus at 104 F straight from the "smack pack." I pitched a yeast starter made from the wort the following day. I'll report back later.
When making a lacto starter, it probably isn't particularly helpful to do it on a stir plate as lactobacillus likes low levels of dissolved oxygen.