So do we have her totally confused as to what works? As for me, I prewash nothing and, unless it needs to be flat, I prefer poly batting. There are some fabrics that I pretest for possible bleeding. I only prewash if it comes from a place that I feel more comfortable that it is "clean" before going into my stash. I like the poofy look of poly batting and it has stood the test of time and use in all the quilts that I've made in the past 10 or more years. As to cotton, I'd want a bit of poly in it as my thought is that cotton will sort of wad and pull apart even within the quilt with future laundering. Just my thoughts and methods. To each his own and your own experience will let you know what you prefer. Since you already have the cotton batt, you might decide to simply wet it and then let it dry and use it. You will find out how you like it for the next quilt you make.