Well, judging from the shape of your model, I think that box mapping would work well, but you might try a planar map as well to see which works best for painting your textures. After you map your model, make sure to save the UVmodel and the map, under the same name in a Folder(usually under the same name). After you've textured and painted your map, you can import your UV mapped model,(not your original model)and then import your textured UV map as a bitmap into Bryce's material editor. Use the default parametric mapping as you apply it and you're good to go. The model should now show up in a render with your texture map applied.