The time has come. This prototype, sleeves and all, turned out as well as can be expected.
(The tights don't have anything to do with anything, I just wanted to see if I could make them. The answer: sort of.)
I still haven't ironed anything, but I did run the pieces of this dress through the washing machine and dry them on the line before using them. It ended up more uniformly wrinkled, which I think counts for something.
I haven't once yet made a closure in the back of these, but this time I did practice the zigzag stitch in place of real hemming, which brought my attention to the fact that I should not do that before cutting the back open and attaching a closure. Had to cut right through that zigzag neck.
(Zigzags instead of hems brought to you by a] my desire for this dress to look rough and worn and b] my inability to cope with hemming a neckline. IT CHANGES THE SIZE OF THE CIRCLE. CAN'T DO IT.)
So. One mostly-correct version done. Time for the real thing.