Painting text shouldn't be hard. I used to inwardly groan at the thought of painting text, but with this new technique, it is simple, accurate and quick to do.
In order to create crisp, proportional text, the fastest way I have found it to use a projector (I have a small one that connects to my iPad). By projecting the text onto the wall, you can then either use chalk to trace the letters out to paint later, or go straight to painting your letters on the wall!
This method increases your accuracy, but also decreases the amount of time and effort you have to put into making the text perfect.