Hi,
I don't know much about skin effects, but is it possible to give the two skins of a model different transparencies and then overlay them on each other, for example to blend two textures or make a shadow-map? I mean without the use of shaders, because I don't yet have commercial edition. I know how to make alpha-transparency, B.T.W, so that's not the problem.

Yup check out Ventilator's AWESOME new plug-in which does exactly that. It allows you to have two separate UV maps. Bummer 3DGS doesn't do this automatically, but Vent's plugin is a great workaround.

http://www.coniserver.net/ubbthreads/showflat.php/Cat/0/Number/755382/