For my cardi that I did which was superwash wool I did pretty much what B describes I think. Although that was stranded colourwork so was quite heavy and lumpy and really needed a good press. In fact the label said do not press. But I did, and it came out just right.
I don't know why patterns tell you to iron things, no knitting book ever tells you to do this, not without pinning them out and putting a damp cloth on etc, but then it's pressing (ie not moving the iron around).
NB you may be right about the stretching as superwash wool is really prone to growing when washed, as I found out with the baby blanket.
Oh, also I own a set of blocking wires which are dead useful as you just thread them through the edges of the knitting and pin the wire in a couple of places, rather than having to use tons of pins.
That's way easier than the lacey top I'm knitting at the moment. Next birthday present project sorted! I even have the right wool at home.
and now know that blocked pieces are much easier to sew together.
