Flat head pins are almost a necessity..
I always wash fabric, (in the washer and dryer and fold as it comes out of the dryer), before putting it in my stash at home and when doing a pattern like the stack/whack, starch and iron it before cutting. "I " haven't had any problems with it being off grain or messing up the ability to line up.. maybe it's the fabric but I would not want to cut and sew any fabric without washing and drying.