Souring a Stout

So I just finished listening to Basic Brewing Radio's episode on Souring a mash.
And I still have a few questions. I am going to do this on my next stout.

#1. They are recommending 5-10% of your mash should be soured for 2 days for a moderately sour beer. With a stout should I be upping this to 10-20% total mash being soured so that the sourness is not covered by the roastyness.

#2. They were saying that the best temp range to get the souring bacteria to work is about 120dF. Should I be cooling the percentage of the mash that I am souring after Sacc Rest and my normal mash? Or should I not be worrying about conversion on that portion and just up the recipe grist to compensate for the percentage that is being removed to sour?

#3. When the portion to sour is as sour as I want it, should I separately sparge this or mix it in with the remaining mash when I am ready to sparge that..

I know that was alot of questions but I dont want to end up with a roasty, nasty sour. Just want a nice bight without the addition to acid or sour malt.

bump? common people

You guys are killing me. Seriously someone must know something about this.

I clicked on it hoping to find out myself. Sorry I've never done it.

I've never done a sour mash, but I've heard results vary widely. In some cases it'll give you a dirty diaper aroma/flavor, in other cases, something along the lines of a nice sour ale. My preferred method is to work with bugs in the fermentation whether it's bottle dregs or Wyeast/WL cultures. I have a big sour Belgian stout that's been souring since December and it's coming along really well. I used a mixture of several commercial sour beers' worth of dregs.

Personally, I think sour mashes impart a "vomit" flavor. I did it once and never again. I'll stick to buying my souring bugs.

I've never done a sour mash. I did leave my spent grains in the mash tun for a few days one time. When I finally got around to dumping them, it smelled like the nastiest vomit I had ever smelled. No way I would ever want that in my beer.

Search for Biermuncher's thread, "I've got the bug". He made a sour mash b-wiesse. I have soured around 16 oz (not quite 3 percent) of O'Flanagan's Standard stout (per his recipe for soured stout), boiled it and added it back to the primary after 5-6 days. I soured at room temp this past spring. It was stinky, but tasting it after the boil didn't bring thoughts of vomit. Anyhow, that stout is over four months old and it just keeps getting better!

I have 9 lbs of blackberries causing trouble in one of my freezers. I have been toying with the idea of brewing a lighter beer, souring 1-2 gallons, boiling, adding to the primary, then racking onto the b-berries in a secondary.

I heard on BBR that that vomit/diaper smell is from to much air exposure to the grain while its souring. But dregs does sound like a good alternative.