I airdry overnight. How dry the hair gets depends on what style you put it in to dry.
I do it b/c I'm laaaazy and 16+ months post. After I DC, detangle, rinse, add products and then re-detangle section by section I'm exhausted.
I do it in two low pigtail/buns b/c my crown and the center of my head us usually in the middle of a regular bun, so it takes forever to dry. If you don't have anywhere to go the next day, you can do more sections and expose more of your scalp overnight to get it drier.
The next day my hair is 90% dry, and already pretty straight because it was stretched overnight. It's also tangle free. I go through in large sections, making sure it's detangled, and then I'll either hit the roots with a paddle brush, or comb through it with the blow dryer for a few seconds. This isn't necessary (unless the roots are still really damp), but it makes getting the roots straight easier, and it makes sure my hair is fully stretched, so I only have to go over ea section once with the flatiron to get it straight.
ETA - I flatiron usually at the end of the next day. I usually wake-up, go about my business, and then finish when I get home, or I wait to do it until the day before I have off so I can take my time.