One of the best techniques for stretching natural hair enough to perform length checks is to roller set natural hair. It is probably the healthiest way to straighten natural hair because of the equal distribution of heat you will receive while sitting under a hair dryer.
Ensure that your hair is fully conditioned and detangled before you begin setting your hair. First, section your hair and then apply a leave-in conditioner to each section. Begin by rolling your hair with smooth rollers, lightly tug at the scalp and roll in an upward motion. Secure each roller with a metal pin. Now, you can either air dry your hair or sit under a hooded dryer for 1 to 2 1/2 hours.
The end result should be billowy, soft and very smooth loose curls that can be worn down on any Hollywood red carpet.