Don’t wash your top & backing before it is quilted and bound, all your seams will fray and create a huge mess. There are a lot of variables that dictate how much a quilt will shrink when finished. Fairly dense quilting will help stabilize everything. Laundering in cold water will also help diminish the shrinking. It is important to follow the recommendations on the batting package- many cotton batting’s say you should Quilt ever 2-4” so that is fairly dense.