I use Quilters Dream battings exclusively and have never washed any. It's bad enough washing fabric and pressing. I know not everyone does.

I love the way a quilt looks, after the batting shrinks just a bit. It just seems to look more natural, that way.

I have only done warm and natural, I would read the package first

I prewash Warm and Natural (or at least wet it and throw it in a hot dryer) to shrink it and it works fine. If the batting is really wrinkled, I will throw it in the dryer with a couple of wet bath towels (ironing batting is just too much work).

I don't prewash anything except for flannel. I also like the crinkly quilt look. I will hang battings from a shelf in the basement to let wrinkles hang out.

It is smart of you to be considering the options beforehand. There are some surprises that are not a good thing! The package should tell you about shrinkage, and you can decide from that. I personally pre-shrink cotton battings, but I don't think that most people do.
Dayle

I had purchased a king sized Quilters Dream batting - took it out of the package to get the wrinkles out of it - the wrinkles never came out - threw it in the dryer to fluff it - the wrinkles did not come out -

Was going to wash it - UNTIL I read the instructions - which were on the BACK of the label - in relatively small print - which said DO NOT WASH - expected shrinkage around 1% - 1% I can live with.

The person that long-armed said it behaved well.

Did not know that about poly batting. Thanks! I love what I learn from this board.