Yes, Artisan further subdivides the proxy and creates a smoother mesh. It does have a paint tool, but I didn't use it on this project (I used SketchUV instead). The proxy models would be too faceted in Thea but I could have possibly used Thea's subdivision functionality to do the same thing. The only drawback is that it would mess up the UVs applied to the models.
In theory you don't need any UV mapping for smooth plastics, but in reality these materials have surface imperfections and scratches etc. so UV mapping your models and recreating these imperfections will result in much more realistic materials and renders.
Check out Bertrand Benoit's recent materials tutorial
. It's V-Ray orientated, but the same principles apply to Thea.