Marius "obliviboy" Silaghi released another MaxScript called Projection Painter
"Projection Painter is a script for 3DS Max which allows you to send a view of your model in your favorite painting application to paint its textures then project them back on to your model."
So instead of projection painting on the 3D model in the viewport, you use photoshop and send it back to your model where it figures out the behinds the scenes voodoo and updates your texture. I also like how it allows you to work around the UV distortion in a model.
It does look very promising and his other scripts are very well written and have some amazing functionality, if you try it out let us know how it goes.
The downside to all the scripts Marius's writes is that they aren't free. But with the insane amount of witchcraft that had to go into creating scripts like these, hopefully you understand that all those frog beaks aren't cheap.