I love sewing with dupioni silk. It sews up easily because it's not as slick as many silks tend to be. And it's just plain nice to touch and handle.
I've washed every dupioni I've worked with. This accomplishes a couple of things--it eliminates the chance of water spotting when sewing or wearing the the garment, and it results in a more "quiet" sheen while still retaining the shimmer of the fiber. IMO, it also provides a more luxurious hand--the texture of unwashed dupioni can be a bit crispy while the washed has more drape.
Of course, you can always have a surprise when washing it. Remember the color shift I experienced when washing these?
The pale chartreuse piece on the right became orange-gold. I'd rather have this happen before making and wearing the garment instead of after!
I wash and dry my yardage by machine after serging the raw edges to prevent fraying. I have a front loader, but other than that, I really don't baby it much. Normal cycle, cold water (I wash almost everything with cold), liquid Tide, Downy Free. And a Color Catcher to pick up any loose dye molecules in the water. Once washed, I throw it in the dryer, normal cycle. I press the yardage after it's dry to smooth it out, then it's ready for cutting.