If I prewash, I just run the fabric through the quick wash cycle with a little laundry detergent. I dry on hot then press on hot. As soon as you wash, the "new shiny" look and feel goes out the window. You can recover some of it by reintroducing spray sizing. The wrinkly look depends on the batting you use, how tightly/loosely it's quilted, and if all parts have been prewashed or not.