This is what the professionals are using, and even when doing
photorealistic computer graphics they are still just using basic tools
in photoshop to blend 3d models with real photos. It isn't hard at all!
And if you want a roll of this paper I have a large roll I could spare.
Or just order direct from the only company I can find that sells this
stuff:
From: http://www.dickblick.com/zz555/07/
Dura-Lar Wet Media
For all of its usefulness, acetate does cause a few headaches - ink
that won't stay, a yellow or grayish cast to old acetate, edges that
curl. The alternatives are expensive and sometimes just don't suit the
purpose.
Dura-Lar is the acetate alternative. It combines the best features of
Mylar and acetate, and offers a variety of products so that you can
purchase the film that suits your needs precisely. It is always
consistent in color and overall clarity, and won't discolor with age.
Dura-Lar is archival quality, safe for overlaying artwork, and it lays
flat. It will remain dimensionally stable for as long as you need.
Dura-Lar Wet - Specially coated on both sides to accept paint, marker,
pen, and airbrush without bleeding, crawling, or chipping. It's
available in individual sheets (larger sizes), in pads of 12 sheets
(smaller sizes), and in rolls of varying lengths and widths.
Comes in sizes big enough to paint a small mural.