While out on the links for a charity golf tournament today, we struck up a conversation with a fellow beardsman. He had just trimmed his beard down a bit and said that one of his reasons was because his longer beard was developing some curls, really more of a wave effect near his jawline that he didn't like.
He asked us how he could straighten his beard the next time he grew it out. In the few minutes we had before teeing-off, here is the advice we gave him.
First, we are generally proponents of embracing the beard you have. Curly or straight, thick or thin, black, blonde, red, grey, and any other variant you have. If you get some curls or waves, they add character to your beard. They make your it unique.
With that being said, the simplest way to remove an unwanted wave from your beard is to use a blow dryer after your beard has been soaked in warm water, like after a shower.
Apply about half of your normal application of beard oil to a still warm and towel dried beard. Then break out a comb first, not a brush. Brushing wet hair has been shown to increase damage and protein loss from your hair, which is not something you want to subject your beard to. If your beard has some length, then comb your beard from the bottom up (teeth toward the ceiling) while running medium heat, not high heat, over the top of the portion of your beard being combed out. If you have a shorter beard, you will have to comb from the top down in the same direction you are applying the heat.
Keep the hair on your beard relatively tight as you comb from root to tip, and don't let the heat stay in one place too long. It may take a couple of passes, but each section should really take no more than 10-15 seconds. I you are only focusing on specific areas, this really will not add much time at all to your post-shower routine.
After you have straightened your beard, add the rest of your beard oil, and comb through your beard to give it the shape you like. You can even brush it now if your beard is dry enough. Add any other products in your typical routine at this point. It's that simple.
For most guys, this short routine will do the trick, there are some more time consuming and radical measures you can take, but they will also be higher risk to your beard.
If you would like to hear more about these alternate techniques, let us know.