dude, try this....
1) render out the front view of the head
2) take that pic file, open it up in photoshop, and on a new layer, paint whatever textures you want using the original render as a template, marking out the positions of the nose and mouth etc..
3) Save this new layer of texturing as its own pic file, open up soft and project this new file on to the head.
4) Make a pure white texture, open it up in soft and apply it to the head as a 2d local UV map, and turn overall blending down to zero...
5) Go to Texture Op----> rendermap
6) It'll bring up a window...defaults should be ok...go OK
7) then PICK that same pure white UV map in the schematic view...what rendermap will do is take a 360 degree snap shot of the entire head as it appears currently with your face texture in place as a projection and applies that shot on top of the white UV map (converts that white into an entire UV map of the whole head as it appears)...the new file should be in the directory where the original white map is stored...you can then delete all your old textures and apply this new UV map as the texture.
There are a few finer details to this method that you should be aware of: one important thing is that rendermap includes all lighting effects when it takes its snapshot, that means shadows and spec highlights will be included in your new texture...sometimes this is cool, but for heads and stuff, usually not since you might want them to react naturally to light sources.
A way around this is to temporarily change the material of the head to a constant material, which wont react to light at all and then restore to its original material after the rendermap process.
I hope you understood what i said...I guarantee the process works...i've used it many times and it works like a charm to convert projections into UV maps..there are other methods as well but this was the one taught to me and I'm comfortable with it...if you have any questions just message me or reply to this post.
Cheers
Bob