Then I make up for the deficiency by placing 2-3 frozen and sanitized 2-liter PET bottles in the wort after I turn the chiller off and stir it a bit.
Making it as simple as possible and headache free is my goal. If it takes an extra 30 minutes to chill the wort the rest of the way with the PET bottles I don't care.
And my beer hasn't suffered one bit.
I was thinking of buying a propeller to stir the pot with a hand drill, but using frozen PET bottles sounds a lot easier. I will try the frozen PET bottles now that my water temp will be over 60 F for the rest of the summer.
I've also used an aeration stone to stir up the wort during cooling (two birds with one stone) but I haven't tried to measure its effectiveness. I stopped over concerns of properly sanitizing the stone.