Begin by gathering enough material to fill a large cooking pot 1/2 to 3/4 full. Dyes can stain your cookware so you may want to select a pot that will only be used for dyeing. I picked one up at a thrift store for a few dollars.

Cover the material with water and simmer for at least 45 min. to an hour. I will sometimes simmer dye material for several hours. You may need to add a little water from time to time as the water evaporates. Don't add too much water or you'll dilute your dye.   

Use a wooden or plastic spoon to stir the material frequently.

Your water should be showing signs of becoming a dye. Some plants make better dyes then others so you'll have to experiment to see which ones work best.

Squish the dye material with a potato masher or any flattening tool to help release extra dye trapped in the material.

Pour the dye mixture through a fine strainer to remove any solid pieces from the liquid. Rinse out your cook pot and then pour the liquid back in. Discard any solid material.

Add 3 tablespoons of white vinegar to help the dye set.

Place your white horsehair pulls in the liquid dye bath and allow them to simmer for a minimum of 30 minutes.

Leave the hair in the dye until it is a little darker than you want your final color to be. (the final color will be lighter after you rinse)

Remove the pulls and rinse under warm water until the water runs clear. To make sure the horsehair is completely rinsed leave the pulls in clean standing water for 10 min. If the water is clear after that time the hair is fully rinsed. With some darker colors you might need to do this step several times. If your pulls are not rinsed properly the colors can bleed later.

Lay your pulls out on a towel or hang them with plastic clips to dry

Make sure you dye enough pulls for your project because natural dyes do not store very well. You can keep the dye in a glass jar in the refrigerator for a month or two. If you want to use it again just reheat it.