Sour mash for Berliner Weisse

I am looking to attempt my first berliner weisse in about a week. I am going to do a Laco starter to throw in at least 36 hours before my yeast hoping to really give it a head start. At the same time I am wanting to do a partial or perferably full sour mash. I have a small grain bill: 3lbs. white wheat, 3lbs. Pilsner, 1 lbs Carapils. My original recipe calls for a 152F mash and sparge with no boil. My question is; can I do my original recipe, transfer to a bucket with 1/2lb of pale malted barley to sour for a day or two...and then I'm stuck. I am doing no boil so do I just transfer full sour mash to my carboy and add the Lacto? Or back to my kettle, raise the temp to kill and unwanted bugs and then transfer to carboy? Or am I off all together? Any help please