Why should I brush or comb my beard?
Brushing is good for your beard. If you're going to brush your beard then you should brush no more than once a day. Doing it more than once a day is over kill to your beard. Brushing too often will create split ends, damaging the facial hair you've worked so hard to grow. Make it part of your daily ritual in morning. For the best results: brush after you shower, for it will make it will make your beard look nice and tidy for the day.
I prefer using combs over brushes since it not as harsh. Plus you can comb your beard more often during the day. However, you can still over comb your beard, creating damage. Combing it should only happen when it gets out sorts through out the day.
What brushes or combs should I buy?
I recommend the Kent Boar Hair Brush. Boar's hair is natural product (sorry vegans) that is not rough on your skin. The brush bristles are uneven so you can reach root to tip in a single stork. Kent also makes a quality product that will last a life time. Yes, you might spend $25 to $200 (expensive brushes are 100% handmade) for a Kent Brush, but you will be using this brush every day. The Kent Brush will probably out live you.
As for combs I recommend either a handmade plastic or handmade wood comb. Kent Combs are simply the best plastic combs you can buy out there. They are handmade, and they care about the products they put out. The comb is first molded, then sawed so the comb has teeth, and finally sanded and polished, making a nice clean looking comb.
SO, why is it different from your standard drug comb that costs $2 to $3? When your cheap drug store combs are made they are molded into the comb shape and taken out and thrown into a bin with 1000's that are just like it. They are not sanded or polished. Which means they have microscopic jagged edges. When you run a standard comb through your hair it will get caught and tug your hair. This will cause unwanted shedding and more split ends in the long run.
Handmade wooden combs on the other hand is more of a style then a need. They are formed from one solid block of wood or two pieces jointed together, and have their teeth sawed into them, then sanded down to be nice and smooth. They are going to cost more money, and they are going to be a special order item from a local wood worker. Expect to pay $75 and up for quality crafted item such a wood comb. The only place I know that has one always listed is Offerman's Wood Shop. Its called a "Mustache Comb," but I would definitely recommend it for someone with a long beard...also who wouldn't want a product made by Nick Offerman's shop?