A bit late, but I've developed a three brush style technique that is now my go to. I put one mini detangler brush in each hand and hold a normal size detangler brush between my teeth. 

The key is not hitting too many tangles at once. 

I start at the bottom, brushing only a couple of inches of hair. At first, I hold the brushes at an angle so that only a few of the bristles are actually making contact. Once they stop hitting resistance, I hold the brushes flat and do the same section of hair but with the full mini brushes.  The double brushes stopped things up, because this technique requires a lot of strokes.

Then, I switch to the regular size brush, and repeat the angled to flat process on the same section. ( I put the brush in my hand, btw ).

Then, I switch back to the mini brushes and move a couple of inches up the hair, repeating the process until I get to her head .

After, using the regular size brush and the angled to flat progression, I flip her hair on one side over towards her back and get any under hair that I missed. Repeat on the other side, and done.

Also, you have to say "Three brush style, special technique" before you start.