Unravel a rope of crepe hair and run it under some water in the sink. Drape it over a shower rod and wait for it to air-dry, which will take about 24 hours. This process will straighten the crepe hair because it will be very curly after you unravel it.
Trim the straightened hair to 1 inch long. Separate the hair into small, even groups that are about 1/16 inch thick and spread them out in front of you to prepare them for application.
Wash your face and dry your skin thoroughly. Dip a small brush into some spirit gum or prosthetic adhesive and brush it above your upper lip, from right below your nostrils to right above the upper edge of your lip. Extend the spirit gum or prosthetic adhesive down at an angle to the corners of your mouth.
Press a group of the ends of the crepe hair against your the skin where you applied the spirit gum and make sure the hairs are applied with an even thickness. Start in the middle of your upper lip and work your way to the sides.
Trim the mustache to the style and length you want