One that I discovered on the rice bags is to only fill it only about 2/3rds. Anymore than that made it too hard. Also, make a double layer of cloth for the bag and use good quality cotton or ******* blend material. You could use your sock as a "pillowcase" for it and remove it to wash.
On a related note, cut a strip of material about 3 -4 inches wide by width of door or window. Fill with rice or beans, sew or knot each end and it can be used as a draft blocker for door or window. Don't use minute rice, not heavy enough.