Just curious, what's the mechanism that causes aeration with the mix-stir? I assume you're putting the mix-stir at the bottom of the vessel and it gets everything moving, maybe forming a vortex?
When I aerate with my mix-stir I will run the blades near the surface for a bit first, which creates a lot of froth. Then I'll drop them lower and create a strong vortex for a bit to 'mix in' the froth. I'll go back and forth between 'frothing' and 'mixing' for a couple of minutes, or until I've got foamy wort right up to the neck of my carboy.
I don't know if that procedure is necessary, but it's worked well for me.
As an aside, I would highly recommend the stainless steel version over the cheaper plastic model. The blades on the plastic version are attached to the shaft with a plastic peg - Perhaps my drill is extra-powerful, but the third time I used my original plastic version that peg snapped. I replaced that with the steel model, and it's still going strong after 40+ brews.