Not all cotton batting is the same. Some is needle punched through a scrim and more stable (the Warm and Natural brand is like this), others needle punched with no scrim (like Quilters Dream brand), some have binders (adhesives) to help it stay stable until it is in the quilt, some don't. Not all cotton battings will hold up to a prewash or popping in the dryer damp as they were never intended to do so.


You need to adhere to the minimum quilting requirements stated on the packaging and remember these are the absolute minimum your quilt spacing needs to be in order for the product to maintain integrity. I usually exceed these requirements and quilt much more. More quilting will help stabilize and reduce the amount of shrinkage. Many times the minimum quilting requirement will give you an indication of what manufacturing process was used. If your minimum distance is 8 to 10" that is usually a good indication that scrim and/or some kind of bonding process was used (but not always, as is the case with Quilters Dream brand which doesn't use a scrim or bonding agent). A minimum distance of 4" may indicate the batting will not hold up well to pre-shrinking. A minimum distance of 2" would definitely mean don't try to preshrink the batting and also may mean the batting will shrink up and give you a very crinkled antique type look.

As far as the "crinkled look" sometimes this is a good thing as it can hide imperfections in your quilting.

As many have said, your choice of batting depends on how you want your finished product to handle. I use 1/4" poly for all my lap quilts, as it drapes nicely and keeps a body warm. I use all-cotton for table runners, bowl huggies or placemats, as it has more body and protection. A wall or bed quilt can be quilted heavily and look wonderful, but I do not find this to my liking for personal coverings. For a baby quilt I also use poly, so it is soft.

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.

Can you tell us what brand cotton batting you got? Or if it's off a bolt, did the shop include a piece of the instructions insert? If the brand can be researched, we can see if it has a scrim, which might indicate whether pre soaking and drying is a possibility.
Personally, I don't prewash my fabric, unless it is flannel. I have always thought that if I ever want to make an "art" quilt, for show more than for comfort, I would pre-soak and machine dry the Warm and Natural batting I use.
The modern quilting fabric we use today doesn't shrink much. The batting will shrink about 5% or so (Guessing). If a person doesn't have anything better to do, she could do a practice swatch, measuring a piece of batting, and hot water soak and dry it, then measure again.

A quilt judge once told me she could spot a quilt made with high loft poly batting a mile away so apparently is isn't a good idea to use for judged show. LOL

I may not know what high loft poly is, but once, years ago, I got some thick poly and did not like working with it. It works superbly, however, for cat mats (flannel on one side, fleece on the other, mildly quilted). I think there is no shortcut for trying different things and seeing what you like for which project.