When I started to be concerned about my brows, I was so afraid to touch them. Fortunately, a friend of my owns a spa and she has looked after setting the foundation in place every six weeks or so. This allows me to just follow the line she has set. Over the past three years she has made my brows a little more feminine. Now I am more confident to 'keep them clean'.
So, after that ramble, my suggestion is to find someone who can give you a good base and can also show you how you can keep the shape. There is a great problem with taking too much out, especially on the top!
All the Best on your journey.