Atpo, I’m not sure I understand your problem clearly but it seems you are asking how to get rid of grid lines from the texture map that UVMapper outputs.

When you open UVMapper texture map in Photoshop, while in Photoshop hit the “D” key to make the foreground color black and background color white.

Then, because the grid lines in the texture map are black, while in PS (Photoshop) in the menu, go to  “Select” and click “color range” adjust “Fuzziness” to get all the black color and click “OK”.

Now with all the black grid lines selected, hold down the Ctrl key and hit “J” key to automatically paste the black grid lines onto its own new layer.

Now, create a new layer between the background UVMapper texture layer and the new “grid layer” and fill this with the background white color. Now you have a white background color under the “grid layer”.

Create a new blank layer between the white background layer and the “grid layer”. On this new layer you can follow the outline of the grid to do your coloring and texturing. Then when finished, make the “grid layer” invisible by clicking the little eye icon to the left of the layer.

This leaves only your colored texture which you can save into BMP, PNG, JPG or any other format you wish to use on your model.