Beard hair is just like the hair on top of your head, only courser, and can be straightened using any traditional hair straightening technique. Most people find that a combination of hair-straightening techniques provide the best results, but you'll have to find the method that works best for your hair. Because beards are so close to your mouth and nose and facial skin are often very sensitive, chemical straighteners are probably not a safe option.
Wash and condition beard in the shower to remove dirt and oil.
Apply a dime-sized amount of smoothing serum to fingertips and run through beard. Use the comb to spread the serum evenly throughout hair. Serums help to smooth hair, condition, and add shine.
Blow dry beard from about 8 inches away while running comb through the length of your beard. Beauty Brains suggest holding your beard straight with a comb while blow drying.
Spritz one to tow pumps of heat protector to beard. Separate into one inch sections. Set straightening iron on lowest heat setting to protect hair and face. Straighten one section of beard at a time, going over hair slowly and repeatedly until hair is straight. Move on to next section until all sections are finished and beard is straight.
Dab a pea-sized amount of hair putty to fingertips and work through beard. You can chunk pieces together to add shape and play up the look. Hair putty will help to hold the hairstyle and prevent frizz.