I picked a Sun & Splash Skipper (on sale at Kay Bee for $4) because, being a teenager, Skipper has a figure almost realistic for an adult. Wider waist, smaller bust, generally closer to human proportions than the standard Barbie mold. And flat feet, too (although that may have been standard for all the Sun & Splash dolls, I'm not exactly a Barbie expert).
The first step was a Cephaloplasty and Brain Transplant. I used an X-Acto knife to cut off the top of Skipper's skull, right along the hair line (the wig created by this currently graces Laser Optimus Prime's head). Then I trimmed down the forehead a bit more to bring it down to more reasonable proportions. Next, I glued a superball into the hollow space behind Skipper's eyes, giving her a brain or sorts. Then I topped the head off with structural acrylic paint (designed to dry without spreading out) in a couple layers, teased out to be like hair. Over a week later it's not totally dry, but it's good enough for painting.
The next step was (after letting the hair dry a few days) to draw Josie's circuitry onto Skipper, using Transformers #9 as a reference (the cover and the big splash page...Manley's art is inconsistent elsewhere) and guessing where I had to fill in the blanks. I had to add extra circuits to the legs because of their inhuman length. Unfortunately, I chose unwisely in using a Sharpie permanent marker for this job, as I'd find out later. Turns out that the ink will migrate upwards through several layers of paint when hit by spray matte or nail polish (yes, I know there's a non-acetone coating out there, but it's a little late now).
I rough-painted over the lines with a brush, two coats over several days. Then I used my fine detail needle to straighten the lines and sharpen the corners. Finally, I painted the hair first with golden yellow, then orange shading while the yellow was still wet. After this dried, I mixed some orange and tan for the deeper shadows, and brought out some highlights with more golden yellow.