This is a great way to place maps and pinpoint areas on the uv surface for texturing. The testmap_help.jpeg shows the testmap used with Photoshop. The steps involves are as follows:

1. Download testmap. Place in a shader.

2. Render the map onto your surface. Use the alphanumeric grid to locate the area you want to texture.

3. Bring the testmap into Photoshop or other paint program. Use transparent layer to "paint" over the area indicated by the render.

4. Save the new map. Replace the testmap with your new map.

5. Rerender your surface.