The longest beard ever recorded belonged to Norway's Hans Langseth and stretched to over 18 feet long. While your own beard is unlikely to grow that much, it will require more upkeep as it gets longer. The Barrington Community Unit School District 220 calculated that it takes approximately 353 days for an average beard to grow six inches. As your beard grows out, you may need to put in additional effort to straighten it.
Wash the beard with shampoo and brush it thoroughly to remove snags. This will smooth it out as much as possible, prior to straightening.
Apply a silicone cream to your beard and run it through the hair strands from top to bottom to straighten the beard more. The cream will coat the hair and make it firmer, allowing it to remain straighter than what it would otherwise.
Comb your hair some more, to spread the silicone cream through it. This straightens the strands and removes excess moisture remaining from washing.
Run a hairdryer over the beard, as you continue to brush it from top to bottom. The drying process helps straighten the beard hair further.
Pull down on the beard and spritz a small amount of hairspray over any areas of the beard that are still not straight enough. The hairspray will further stiffen the hair to keep the beard straighter for a longer period of time.
A flat iron can also be used to hold a beard in a straightened position, if you wish to invest in one. Always use care to not burn yourself when using a flat iron and follow all operating instructions.