About once a month I cut my brows, this isn’t necessary for everyone, but for me it is. I brush up my brows; use whatever you want e.g., a mascara brush, then just cut along the top with nail scissors.
An essential step for us is plucking I use Tweezersman tweezers, but you can you use whatever you want whether it is using tweezers like me, threading, waxing (at home or professionally), whatever. Just keep in mind the rough rule of where your eyebrows start, finish and where your arch should be (shown below) but keep in mind if it naturally it isn’t there don’t push it (as you can see mine aren’t within the lines nor are they symmetrical). My rule is less is always more because I’d rather look like Zachary Quinto than the Evil Queen.
Another important factor is colour for years I hated they way it looked if I did my brows and when I found the right colour it just looked natural. They key is going cool, it doesn’t matter if your hair is bright orange cool with always look better than warm (don’t ask me why just that it does). I personally use a black eye shadow. I know black, I always thought it would look weird too but it is only colour I will use. I have naturally very dark eyebrows but light-ish brown hair. There’s meant to be a rule of if your blonde go 2 shades lighter, and if you hair brown hair two shades lighter, but just go with natural colour of your brows it will look best (unless of course you’ve died your hair a drastically different colour).
I use a very light hand, and light brush for it. I use an E70 from Sigma, which is a medium angle brush far lighter and bigger than your average brow brush. I lightly brush this all over my brows, which fills them out a bit (not that I really need it) and takes away any gray cast foundation might leave on the brows.
Then I go in with a smaller brush like an E65 from Sigma, which is a small angle brush. I use this to fill in the end of brows because I went one snip wrong and have had to fill them in like this for the past 3 weeks (see what I mean about the Zachary Quinto thing).
Lastly I just go over my brows with clear mascara, but you could go all fancy with a brow gel (coloured or clear, I think clear would work best, especially if the powder matched perfectly).
For extra definition add an off white under the brow which gives the effect of a stronger arch and that’s it.