What do you mean, it's taking forever? Which part, or do you mean theme development in general?
Coding, and in this case specifically front-end development, is a slow thing. There is just a lot that needs to be done and it takes a while. With experience you'll get better at it but there is no magic way to improve your performance.
You can, however, improve your both your speed and code quality quite substantially by using a proper work environment, starting with a good IDE.