I swear by this method, I am 12 months post, and washing in sections has allowed me to hang onto my relaxed ends, avoid splits, and my "detangling" time is around 5-10 minutes for my entire head.
I usually wear my hair straight so pre-wash it is already detangled. I part my hair down the middle of my head (hairline to nape), and then further divided those halves into 3 sections each. This leaves me with 6 sections. I have experimented with smaller sections, but 6 seems to be the magic number to allow me to adequately get to my scalp, smaller braids tend to be too tight for this.
I leave my braids in for the entire washing process, prepoo, shampoo and deep condition. This is key! My hair never ever gets a chance to tangle through the entire process, so combing at the end is so easy! I was skeptical at first about DC'ing in braids, I wasn't convinced that the product would thoroughly coat my strands, but it works! I use an applicator bottle with a nozzle to get down near the roots, and I always DC with a hooded dryer so this may help the product to adequately reach the inner strands.
In the end because my hair never had a chance to tangle, "detangling" is as simple as running the comb through each section to get rid of any minor tangling, and then I run my knock-off denman through to remove any shed hair. It takes 5-8 minutes, at the most 10 if I had been wearing a textured style the previous week.