I do per-wash to get rid of any chemicals in the fabric, this is the time you would want your fabric to run or bleed loss dyes, not when you have all ready done the work in sewing a quilt of any size! If you chose not to wash you could always test the fabric first with a wet cotton swab, but then it would get rid of the chemicals in it. I use spray sizing just because I like all that is does for me as stated in others posts. I also think that fabric doesn't always shrink the same, this way the shrinking is done with and your quilt if washed ever won't go wonky! P.S. there are no dumb questions!!