FYI 2 days ago I brewed a 5 gallon all grain. After the wort was chilled to 70 degrees, I attached an oxygen tube to my racking arm that came with my original brewing kit. I turned on the oxygen and lightly stirred it all around the wort as the oxygen bubbled up through. I only did it for 1 to 2 minutes. Pitched my rehydrated yeast and put it away to ferment. Less than 12 hours later temp was up and the airlock is bubbling nicely, its doing it so well some foam is coming through the airlock. My point is, I ve done a bunch of batches with just stirring the hell out of the wort and the oxygen seems to make all the difference.