I go form a poly cube make a base mech then inpoty into Zbrush sculpt, then export and UV then re-import as a morph target (not too sure if this is the best way, just that the base topology can move when sculpting and mess with the UV's).

I then either texture in Z poly painting/Projection brushing using a combination between Z and PS.

As Jay and Funkey said, getting a nice base mesh is the way to go.