I haven't done much in the quilting yet but will. As to weather to prewash or not. A solution to the tangled mess that can happen. As I purchase my fabric, for what ever reason, I serge my raw edges before I toss in the washer. You won't loose threads. Also toss in a dye graber in so as not to have fabric bleed. Ironing, which I do not mind, spray the fabric with Mary Ellen's Best Press & it will handle quite nicely. Enjoy.