I prewash everything, even prior to making a rag quilt. I have used 1/2 inch seams for my rag quilts, which works quite nicely. We don't have a laundromat near were we live, so I used our home machine and checked the filters frequently. I also used the vacuum to suck up threads. Your big bag idea sounds workable...I didn't put any of mine in the dryer (in Australia we line dry a lot). Checking the lint filters is really important, you don't want to have a fire start in the back of your dryer. Don't forget to show us when you are done....We looooove pictures.