For the pistol Wraith, I tried to make it look like it was coming out of incorporeal. It turned out a lot softer than the pictures show, and I am pretty happy with it. It doesn't show up in the pic but the greenish blue is glossy and the front half is matte, which gives it a cool dynamic.
The one year mark of the blog is coming up in a few days and to celebrate I will be doing a tutorial (which I haven't done in awhile) on how to paint ghostly/incorporeal models/units. Until then, happy gaming!