Doug...
Do you mean making photorealistic images from scratch or from photos? I myself vote for either.
I don't have any techniques to contribute yet... but an observation. I came to this forum from the WetPaint forums. There I mainly hung out at the airbrush forum. I am a relative newbie to both airbrush and photo manipulation having used them for things other than fine art. Having recently purchased a large number of restored antique digitalized photos with the intention of printing them and hand tinting them, I have sought techniques and now see that hand tinting may be a thing of the past. Don't get me wrong, it probably has its place for historical restoration or for demanding a higher price, but how many consumers could really tell the difference.
There are many fine photorealists at WetPaint. There many talented manipulators of images here. It's interesting that one discipline tries to imitate the other. It was a little ironic that when I started getting into the forums here people are trying to turn perfectly fine images into surrealism or pen & ink while on the other site people were trying to go the opposite direction. I can appreciate both goals.
And then the age old question of

"What is art?" always comes up.
I myself just like all the "purty pictures".
...Kent