This is a follow-up to this question: Long cooling before pitching -- read that for background.
I aerate to add oxygen to my wort by pouring back and forth between buckets. If I wait before pitching, in order to cool the wort further, can I aerate the wort before putting it in the chiller to cool? I have been waiting until after the wort cools completely before aerating.
Well your aeration method will be more efficient if done while cool. As the warm wort won't hold as much dissolved oxygen. Furthermore, the warmer the wort the faster oxidative (staling) reactions will occur.
When I make lagers I chill with my IC down to 65-70F, transfer to my fermentor then put it in my fermentation fridge overnight to get it to 50F (fermenting temp). Then I aerate (oxygenate actually with pure O2) and pitch yeast.
So in my opinion, its best to aerate while cool.
