I did a 6 page tutorial for the former German Advanced Photoshop magazine (then"bildbearbeiter" now "pictures") the url changed, but the workshop is still downloadable, thanks to the way-back-machine, you can find and download the full article here: https://web.archive.org/web/201301
(Interesting for German readers only - sorry.)

The complete workshop covers how to create the tubes with the pen tool and how to achieve the mechanical cyborg-skin-look.

I have put a little overview / walkthrough on my blog here: http://www.fantasio.info/2012/04/

All image credits are mentioned and used with permission, the model is courtesy of mjranum-stock.