This has been elduing me for over a decade!

Is there a program:

1.  Load your obj or cr2.
2.  Be able to turn off any parts you're not texturing
3.  Apply a MAT pose for a base texture, if desired
4.  Take soft selected lassos of existing photograph and project them onto mesh
5.  Repeat step 4, preferably in layers, rotating camera around model for best placement.
6.  Bake it into map using established UVs
7.  Fix it up in Photoshop.

It just seems to me there's no reasonable way to do this without a program such as imagined.  V4's UV's snake around and divot and cruch up over an area as crucial as eyebrows, for example, and this is totally unsatisfactory with trial-and-error in 2d!

A few existing things I've tried either make low-res maps, no good, not even for reference, or simultaneously make morphs which are unusable but change the placement of what you've projected.  (Yeah, you, faceshop...)

Please advise!

-WTB

 Right Hemisphere Deep Paint (old though ... one of the new options is better)

Body Paint (by Maxon), which also comes with Cinema 4D

Autodesk Mudbox

I know you can also texture in ZBrush, but not sure about the turning parts on or off bit ... someone might confirm

(the MAT pose, no ... but you can load in a texture to start with)

 And, knowing you're a morpher, all three of those options also allow you to morph and create displacement maps also.

It seems like I've tried all of these over the years, and none of them really delivered.  either the process was way too complicated, the software too crashy, or the whole thing really not designed for poser users in mind.  Further, the projecting of soft selected lassoed samples...I've not seen that. 

Displacement maps are further down the list of things I'd like to accomplish.  I do all my morphing in poser, with stock morphs and magnets.  I just need this projection feature

Deep Paint does that, but it's SOOOOOO old now that I hesitate to recommend it. It does have issues that the newer software handles much better, and also doesn't let you morph. Plus, if you are doing multiple 4000x4000 face texture maps (diffuse, bump, shine), and then start adding body textures and its bump and shine, your system slows to a crawl with it, because it treats them all as 4000x4000 textures.

Also Deep Paint doesn't do displacement IIRC ... does do bump though.

I know a few around here have recommended Blacksmith 3D, but I've never used that one.

There are lots of 3D painting programs that allow the use of photographs, including 3DCoat. Features like switching off parts you're not texturing, lassoes... I dunno.

Check out Blacksmith3d and Blender2.49

Blacksmith3D is Poser figure friendly and has a freeware version of the paint portion of the suite so you can try it out.

Blender2.49b is free, handles projection painting pretty well but is less than Poser friendly ATM.

You can paint on a 3D model in Adobe PhotoShop CS4 Extended also. However, it is still an immature addition to PhotoShop and kind of a PITA to use.

I've made a remap of V4.2 which will allow you to texture her with V3 style textures, and to also make new V3 style textures for her.  I'll soon be marketing this model at Content Paradise.  My version of this figure should ease your problem considerably.
Also, the figure will be V3 MAT file posable.
If you'd like to help make me some publicity renders of her, I'll be willing to send you a copy: dphoadley2@yahoo.com
DPH

 Blacksmith3D, as mentioned above, can paint with photographic textures.

It's really a great program both for morphs and for textures. I have a little trouble with their newest version though so I'm still at Blacksmith3D version 2.2.

I think the OP is aware of numerous programs that can paint with photographic textures. He just has some additional requirements that he hasn't found....

Attached Link: http://www.3d-coat.com/

I find 3Dcoat to be the best one I have used. the newest version is very easy to use. Fugazi1968 has loads of tutorials for working with Poser.3Dcoat paints over seams. You can turn off parts.   The other benefit is you can go directly from Poser or go through UV mapper and choose only the material zones and body parts you want to use. It is simple to work with Poser characters in 3Dpaint. cheerio lululee

Believable - You are correct, I've tried just about everything...however...

Lululee - I have not heard of 3d-coat, will definately look into that, thanks!