I know some say it's not the size of the tool, it's how you use it. But so far, I have not been able to figure out how to use a large brush to fill a tiny precise corner of canvas. Its like trying to hammer a tack into the wall with a mallet - it just doesn't work.
So now I'm sitting at my easel all hunched over, trying to work these tiny brushes into tiny corners. It's still kind of driving me crazy because I hate to work that tight and tense. But - I am making progress, which is fabulous. Guess I just needed the right sized tool for the job. Sometimes smaller really is better. ;-)