I've taken two workshops with Debbie Maddy. She is a great instructor, easy to listen to and super nice. She knows her stuff and has funny stories about traveling. Don't hesitate to take one of her classes.
What helps me to keep my blocks all the same size: I starch my fabric stiff as paper before cutting. I use a seam guide that is exactly 1/4" seam. I sew very slow. I use thin thread for piecing. It takes time and patience to be accurate.