I have never done a sour mash, but many reports use 'vomit' to describe the smell. If you are going to use a lacto culture, why use the raw grain? That way you can avoid culturing clostridium which, I believe, is the source of the awful smell.
If you use the lacto culture, I would taste it before adding the yeast to make sure it is sour enough.. It can take a while for the lacto to get going. You really want it sour before you pitch the yeast as the alcohol will slow or stop the lacto. If you use grain, I'm not sure you would want to taste it.
I've done 2 with Lacto, and they both took 5 days at 95 F to get nicely sour.