Many people ask me how long it takes to grow a respectable handlebar moustache. When I say, "about three months," I can see crests falling. There are a few points I would like to make about this. Just because your handlebar moustache is not fully mature early on, it doesn't mean it looks bad right up until day 90. In fact, it can look pretty decent all the way through the growing. During the growing period you may end up using a little extra wax to keep untrained hairs out of your mouth. Yes, I said untrained hairs. Unless you have had a handlebar for a while your moustache thinks it is "business as usual" and will grow is its natural pattern. It may surprise you that lip hair has a pattern, but just like the hairs on your beard or your head moustache hair has a preferred growth pattern. This three month growing period does two things. First, it allows the inner hair to catch up to the outer hairs. Second, the time period allows the wax to train the hair to go the direction you want it to grow.
These are all optional but may make you feel more comfortable joining the handlebar moustache fraternity. Use what you like and ignore the rest.
Like the tricks, above, these are guidelines I am offering to you, man-to-man, not rules. Experiment and let me know if you find a better way!
I advise that you give it two to three weeks before trimming any hairs. If a single hair is driving you nuts--guillotine it, but if you can bear it, let them all grow until you get a good idea of which hairs will play along and which ones need to go. I strongly advise against cutting the hairs directly above the lip (which you are used to cutting if you have a goatee now) because then you end up with a handlebar mullet! You want those hairs to grow out and meet the outer hairs in order to get that full and natural look. After a couple of weeks you will start to notice that some hairs just don't belong. I have a few that grow North of the main part of my moustache that just never blend in well, so I trim them with little, sharp sewing scissors. I also trim a few hairs right beneath my nose for the same reason.
Now this may be controversial, but I noticed that sometimes not matter how much I fiddle with my handlebar or applied wax, the ends tended to curl out to make bull horns (and these do not look great and photograph even worse) or one handle would get bent the wrong way on my pillow as I slept, so I turned to extreme measures. I used a DIY moustache snood while sleeping for a few nights in a row. I went to the drug store and picked up, for a few bucks, a package of nylon stretchy headbands with the little rubber nubs and wore the bad around my moustache and then around the back of my head where that line is under the bump on the back of your skull. This wasn't too tight for me and is reportedly not amorous in nature, but gives you eight or so hours (while sleeping) of hard core moustache training when needed. I have only done this a couple times.
If you are using wax, you will want a dedicated comb so that you don't get wax in the hair on your head when combing it. (This doesn't apply to me exactly, because I am bald on top and keep the remaining hair short.) You will find this accumulates wax, so run it under hot water and use some good dish soap (I like blue Dawn) and a badger haired brush or old tooth brush to clean up the residue here and there. Pro-tip: Blow brying your combs to melt the wax and then wiping on a paper towel may sound like a good idea but then your comb melts like one of Dali's clocks and that will not help you grow Dali's moustache!
Hairs will fall out and though it can feel like a setback when you have been spending so much time and energy to get long curled hairs, know that it is normal. One caveat: if your moustache has a heavier coating of wax on it, don't pull a comb through at room temperature because in this specific scenario you may actually be pulling some "live" hairs clean out of their socket due to friction. I recommend cupping your hands and breathing that deep warm lung air into your moustache before combing or passing a blow dryer on low heat over your moustache a few times to soften the wax before combing. This is especially true of stiffer waxes.