I usually have my eyebrows threaded but I actually haven't done in a while so I have been plucking them; which I actually hate doing but what can ya do! Threading does hurt but for me only as much or less than plucking and the results are totally worth the pain; my eyebrows always look so much better after threading and they shape them much better than I can ever pluck them.
As for filling in eyebrows, I used to do it sometimes with powders but I wasn't very good at it, my brows were sometimes uneven NOT A GOOD LOOK. I think everyone knows that eyebrows should be sisters and not twins, but it isn't at all attractive when they're distant cousins! Personally, I find it really hard to fill in my eyebrows really well, so they are an even and good shape which isn't too different to my natural brow.
So, I tried these EyeBrow Shaping Stencils from elf.com. They cost £1.50, so I thought I may as well "guinea pig" them!