As you grow your beard out, you may notice patchy areas where the hair just isn’t growing in all the way. Let it grow. One of the first things you have to do to fill in a patchy beard is to resist your urge to trim it and just let it grow. In addition, you need to take good care of your facial hair by following a routine and embrace what you have. Eating a good diet and getting plenty of sleep can also help the facial hair along the way as well.