I came across another texturing program tailored for artists and the movie industry
but it's actually fairly cheap online compared to some other programs. $190 academic and
just under $300 retail.
The program is Maxon BodyPaint 3D, and allows you to not only paint directly
on the model, but also in an active rendering mode so you can see just what it will look like.
It supports Max and a few other modeling programs, as well as Photoshop files and similar.
It can take care of the bump maps and several other texture types (shine, diffuse, color, etc).
I've only been messing with it a few minutes, but I can already see there is a vast similarity to
Photoshop's painting, layering, and filter system. Pretty much if PS and Max had a child, this would
be darn close and it's somewhat easy to pick up and draw. Comes with UV editing tools and
some basic model editing tools all together in a tidy package.
There's a demo on the Maxon site.
http://www.maxon.net/pages/products/bodypaint3d/bodypaint3d_e.html