I replied to this post, but I must of had a couple beers in me because I don't see my reply. Opps. Here is the short, short version.
UV editing in Softimage is very flexible. You can get creative in your approach so try these ideas.
First, I will add that a very nice plugins exists at www.cineframe.com, called YouMap it's $99 and worth every buck. The idea its that you can map polys using the UV's of a nurbs. Very Nice. Instead of using it as demonstrated on the site, I use it to "flatten" my ploy mesh. I wrap my nurbs grid around my mesh, then use the Paint Dialogue to move the UV cords to my liking. Then stamp and paint.
BTW the G, Shift+G, H, Shift+H, S, T, and Shift+T, are used to Select/Deselect/Toggle polys, All Polys, Highlight/Unhighlight/Toggle polys, All Polys, Select or Hightlight only polys with the assigned texture, Tag/Untag/Toggle Points (all the UV cords in the clip window or individual UVs in the 3d window), All Points. Use these keys and follow the command bar options.
Here is another method. This is the break up technique. When your done modeling your mesh. Freeze transformations. Then Select and detach pieces. Actually in is easier to duplicate your object and delete parts, because using the poly detach function explodes your mesh object into individual polys; so you have to use the cleanup function to fuse the edges of your detached piece, which is an extra step. Either way, break up your mesh into pieces that you want to lay flat. Make a copy of the pieces. You can now use the Deform>unwrap, any STR's, Deform>by Surface, Deform>Shrinkwrap,....anything you want to move the copies to a flat plane. Or use any mapping method you want, they don't have to be on a plane. I use a flat plane to arrange my meshes into a single texture sheet for game models, but you don't have too. You can now map away. Use the Paint Module for UV's editing, use any mapping projections, freeze the projections, use as many materials and different shading models as you need.....whatever.
When your are done mapping (or you may use this technique to arrange UV's for painting your model later). Select the copied, distorted and translated, piece and shape animate it back to original form by using Shape>Select Key Shape and picking the similar unmodified piece. Reset the transformation with Effect>Rest Transf or manually zero out Rotation and Translation; set Scaling to 1. Now your textured (or UV manipulated object is resting over your original piece. Do the same for the other pieces. Last step is to unify these pieces again. Use Effect GC_Merge. GC_Merge respects all the UV edits, Textures, Materials, Projection Methods and Shade Models you assigned. Kewl huh.
And then you can use RenderMap....but my beer is empty, so another time... Hope this made sense. Experiment with some of these ideas, and you will easily find your own methods. Good Luck.
-lard