I have a long, bushy beard (and curly handlebar moustache)

First of all, the hard truth is that not everyone can grow a decent beard. Vitamins, diet, etc. certainly won’t hurt, but at a certain point you’re up against genetics, and if your DNA says your beard is going to be thin and patchy, there’s not much you can do about that except maybe hair transplants.

Age plays a factor, I have a friend who couldn’t grow a decent beard until he was about 30.

Now assuming you’ve actually got enough hair growing in the right places

Most important is keeping it trimmed and neat-looking.

Until you’ve got a couple inches of beard going, I think it’s best to keep your neck shaved, pick a point maybe an inch or two above your Adams apple, and keep everything below that shaved. Once you’ve got some beard going you can stop doing that, no one can see it anyway and at some point the neckbeard just becomes more beard.

Similarly, clean up your cheeks. You probably have a few scraggly hairs growing up above the rest of your beard, shave those off.

If you’re a little brave, a straight razor is pretty nice for making some clean lines, you can be really precise with them. They make ones that use a disposable Blade if you’re not into all the sharpening and stopping that goes with a traditional straight razor, I have one that uses a double edge blade snapped in half (they break very cleanly) but most of the time I just use a regular safety razor, or a disposable or cartridge razor would do the trick just fine

Especially when you’re starting off, a beard trimmer or hair clippers are gonna be your best friend so you can trim it all down to an even length.

Figure out what you’re doing with your sideburns. I shave my head, and ideally I like to have them fade into that, but I’m cheap and lazy so I only go to my barber to have that done a couple times a year when I need to look good for a wedding or whatever. Most of the time I just take my clippers to them and try to make them shorter up top and longer towards the bottom, it takes some practice and playing with the guards and such, and I’ve actually gotten pretty good at freehanding it, but it’s not the fancy fade my barber can manage.

Once you’ve got some length, things get kind of easy, I tend to go for a longer, sort rectangular shape to my beard, I brush it out, and basically just cut off anything that isn’t where I want it to be and any split ends d notice.

For soap/shampoo/conditioner/beard oil/balm, etc. you kind of need to figure out what works for you and your hair/skin type. My hair and skin are pretty forgiving, I could probably just about shower in acetone and be none the worse for it. I shower with doctor bronners for no particular reason other than I find their peppermint to be refreshing and I can buy it in a gallon jug, and since it’s pretty concentrated a little goes a long way and I don’t have to buy soap for a couple years, and I don’t personally find any need to use any conditioner or beard balm/oil, etc. Other people find that Dr Bronners it really dries out their skin/hair so YMMV. I also find that it’s pretty good at stripping the wax out of my moustache.

I do sometimes use beard balm/oil for special occasions to help tame my beard and give it a little extra shine. I rarely buy it for myself, I find that once you have a beard it tends to be one of those things people gift you at Christmas or whatever.

I use Firehouse Moustache Wax (specifically their Wacky Tacky) to curl my moustache. That’s a very stiff wax if you don’t intend to curl it. I haven’t tried their other waxes but I’m sure they work fine for general styling. It’s the second wax I’ve tried, I find it works well, and I haven’t felt the need to experiment further. The first one I tried because it was readily available at CVS at the time was Clubman, that stuff is garbage. Doesn’t hold well, and if you get even the slightest bit wet or sweaty it washes right out. I also remember it having some sort of scent, which I’m not particularly a fan of for something that lives right below my nose.

If you’re not going for a full Snidely Whiplash curl, some other lighter wax or maybe pomade is probably worth keeping around to help tame and style it a bit. I have a tin of Murray’s pomade I keep around for that purpose though rarely use it. A little goes a long way with that, otherwise your beard gets kind of greasy and sticky.

I spend very little time on my beard. I brush it every day, wash it when I shower (usually every day, but I’ve been known to skip a day or two here and there,) clean up my cheeks when I shave my head (once or twice a week) and style my moustache mostly every day (it only takes a couple minutes, the Wacky Tacky is very stiff, I rub some into my 'stache, run a comb through it to help distribute it through a little better, and then pretty much just mold it into place with my fingers,) and do a little trimming maybe every couple weeks or when I notice it’s getting a bit wild looking.