By request, below is my old routine for doing a blow-out on natural hair. I only straighten my hair a couple times, but you can do it as often as you like. I use a blow-out regimen that involves stretching and air drying the hair which allows for less potential of heat damage due to using minimal amount of heat.
1. Wash, condition, detangle and deep condition hair.
2. Apply silicone based heat protectant, I have no real favorites any brand will do. Silicone coats the hair protecting it from heat styling and humidity in the air. If you are CG or wanting to use natural products then use grapeseed oil which has a very high smoke point so it is safer than other oils such as olive or coconut. You can also use a shea butter mix as a protectant.
3. Braid hair into 6-8 plaits and allow to air dry. This will stretch the hair.
4. When hair is about 75 -80% dry, take down each plait one at a time and blowdry each section in the DOWNWARD direction. You should blowdry using either a comb attachment or using a denman/paddle/round brush to provide tension. You can use a concentrator nozzle to help make even quicker work of it just be sure to keep the dryer moving and do not leave in one place for more than a few seconds.
It is the TENSION, NOT THE HEAT that elongates the curl pattern. Because the hair is mostly dry you should be able to blowdry on low to medium heat and still yield straight results in no time. If you choose to use high heat do so sparingly as not to fry your hair. Before finishing each section be sure to use the “cool” button to go over the area.
This blowdrying method alone does not yield bone-straight results, but it works for me. If you are going for a bone straight look you can follow with a flat iron. Remember that when using silicone product you will need to use a sulfate shampoo to properly cleanse your hair.
It takes some practice to get the technique down but you can do it! Else you can go to a salon and have it done relatively inexpensively. For an even better deal, visit your local hair school.