It didn't take as long as I thought it would and it wasn't very hard standing still during the process. With "Pride and Prejudice" running on DVD in the background, it all turned out to be a quite enjoyable experience.
I won't write any step-by-step instructions because those already exists, and way better than anything I could produce. See, for example, here and here and here.
My stepdaughter is very petite and I'm... well, not, and we used up two rolls of tape - altogether 100 meters! My double ended up a bit larger than I am, about two centimetres extra in waist and bust, but overall I'm very happy with how it turned out and I think it will be of great value during future fittings. And as I said, very fun to make! It would make for a great "party" with a bunch of friends (who would actually want and need a duct tape dummy, of course).
And some pictures that I probably will regret posting, but here we go:
I have about one layer of tape on my body here. And loving it! As you can tell.
Two layers. Warning! This be my seductive look. Don't view this picture too long if you're easily aroused.
Two layers. Warning! This be my seductive look. Don't view this picture too long if you're easily aroused. 
The finished product, not yet completely stuffed because I didn't buy enough stuff to stuff it with.
