ok, so I'm mega biased with brows because I love the korean style straight brow. >>810
this may help you too.
My natural eyebrow has an arch to it but you can essentially get any eyebrow you want by using a brush, one of those little single blade hair trimmers. You can get this stuff very cheap. You will also need a natural toned eyebrow pencil, and sometimes a light mascara can help add "natural" looking fake hair haha.
The easiest way I found is to draw the ideal eyebrow shape with a sharp eyeliner pencil, see what hair combs into that shape (you'll find yourself combing parts up and coming parts down, I have to comb my arch down and the bits at the centre of my face I comb up ahaha). Then use the razor to trim around the outside of the shape. Sometimes this can be a lot of hair, sometimes it's not a lot at all, depending on how much your brows grow etc.
Once you have done that, fill in the shape with a pencil lightly
. you can be a bit darker with the strokes in more "bald" places, but I usually try and use a mascara for these bits.
There's a lot of images online if you google "korean straight brow tutorial" but from experience of my friends and I, you're luckier if you have thinner brows to start with. It also means you can see better if brow starts to grow back in more scarce areas!
I've badly edited a shape over in paint, photo attached. As you can see, on the right brow there may be more hair under the desired shape, but it's okay.
I hope this helps you guys anyway <3