Either way works, looks like you make every effort which is commendable.
When prepping new fabric I wash in warm with baby clothes detergent & a color grabber sheet for any that may bleed onto other fabrics in the wash. Haven't had a problem yet maybe because I only use quilters cotton & don't overcrowd in the wash? Not fond of the sizing or whatever manufacturers put on the fabric, yuck! Best Press seems to work best when ironing before cutting. When the quilt is finished I wash in cold water & same detergent in a front load machine & toss in another color grabber then hang across 2 or three lines on the clothes line out back in the shade or use a gas dryer on low, takes about the same time as hanging outside so depends on the weather.