In most cases the easiest approach is not to use Truespace at all. Instead, get hold of the last free release of Lithium Unwrapper 1.3 . Use that to uv map your model and produce template textures. Then paint up the template textures in a paint package of your choice.
There are only a couple of reasons ever to drop back into Truespace:
One is repeating textures. Sometimes you can do repeating textures by piling up polygons on the same part of the uv map. Sometimes this doesn't work. You'll know when. In this case you make the repeating texture into a seperate texture file and use Truespace's repeat and offset properties. You have to set those in Truespace.
The other reason is to do with smooth shading. I think models created in Truespace are textured with an auto-facet smoothing material by default. They keep that when you work with them in Lith. That's fine as PCS automatically smooths models with the auto-facet property. If you want to ensure that PCS doesn't smooth a polygon then you need to change it to faceted (or ironically smooth

). Either will stop PCS from auto smoothing the polygon. Bearing in mind you're only allowed 1 group of smoothed polygons. In any event, you can only change the smoothing property in Truespace.