title_body: When to use stirring to increase extraction?
upvoted_answer: Stirring should be used if the grounds were not evenly dispersed in the beginning of the process for some reason (in immersion brewing methods).  For instance, when I am using my pour over at work, if my initial pour leaves some dry spots floating on top.  The Aeropress uses stirring prior to extraction presumably because the short time combined with the tube shape (narrow with all the grounds at the bottom) demand a good mixing.  I've seen many badly designed drip brewers that leave a chunk of dry grounds in the basket when done.  This is because the drip isn't dispersing water evenly and some of the grounds end up wasted,  finer grind, longer brew and temp won't necessarily help bad engineering in that case.