I don't know if pens do well on starched fabric. i know it's best if you dont' use fabric softener if you wash the fabric before making it into quilt blocks.
freezer paper ironed onto the back of the blocks will help keep them stable and good for signing.
Micron pigma pens size .05 are good. i heat set siggys too just to be sure. I' ve also used jelly roll pens. they must be fabric safe and permanent.
wrap your blocks with cling wrap or put in zip lock bags. not bags that have that thick zipper thing though. not good for mailing.