We have been using the KitchenAid Mixer for making Chapati dough for a couple of years now. I know kneading the dough for chapatis is not a very easy or interesting task. Here's how I use this mixer to make our life a bit easy: -
1. For one cup wheat flour, use a little more than half-cup water. If you mix any other kind of flours like buckwheat, millet (jowar/bajra) you will need to use less water.
2. Knead the dough on the lowest setting. Use the dough-hook attachment.
3. Once it forms into a ball and hangs from the hook, check the firmness and knead for another minute or two.