I tried hand quilting without a hoop, but found my stitches were much better when using a hoop.
I took a hand quilting class that taught me to keep the quilt loose in the hoop. You should be able to depress the middle about the width of a fist (3 or 4 inches). That slack allows room for the rocking motion.
Both hands are important for making this stitch easy to do. The trick is learning to use the hands together.