Remember that you can also use layers and stuff. Put the UVMapper output in one layer, in a distinct colour, and the texture-map in other layers. Base colour in one, details in another, the bit you're working on in a third. Adjust the transparencies of the layers so you can see the mesh. Choose colours to make the details you're editing clear, rather than working with the final colours. Use the polygon mesh of the UV map as a texture and save those renders so you can relate the mesh to the object. Do a render with a checkerboard texture to get a feel for the flow of patterns, and the distortions. A lot of this is equally applicable to transparency maps, which are used to modify clothing. And, while I've not tried it yet myself, bump/displacement maps can give you those small changes at seams and hems, or for pockets. I don't claim to be an expert, but what I found is that it pays off to practise doing this stuff, and sometimes you need to go and look at the tools the paint program gives you and forget about Poser for a while.