I'd go as far as saying UV Mapping is an art-form in its own right...

Kudos to modellers who bundle templates: May the Force be with You !!

I do a lot of 'fun' porting from eg SFM, XPS & PMX formats. eg Free Noesis can extract SFM textures and mesh, but you're left to match them up. And, internal flags such as scaling / wrapping controls are lost. I remember spending a lot of time trying to get an SFM MLP's eye-textures to match port. Okay, Poser's material room has many arcane options and controls that I'm still discovering. I prefer to have OBJ+MTL files I can grok. IIRC, after umpteen hapless attempts to re-map the model's topology, which all 'broke' the well-mapped 'body-textures', I threw finer and finer 'finder grids' at the problem. Found each 'eye' tucked away near corner. 'Iterated' scale and ovality, got passable results at expense of a migraine. Is not 'right', is on my 'ReDoBetter' list, but...

Another head-scratcher is UV mapping scenes' luminaires so you can mask the glowy bits correctly, dial them to super-ambient / set emissivity etc. Easy when a luminaire's light-source has own material. Yay !! Harder when pendant, bracket, conduit, switch share map. Hard when map covers multiple items in multiple locations, is 'very busy', and the lights' contribution not obvious. I iterated one such into submission by re-painting mapped texture's likely zones with vibrant hues, looking to see what appeared where. The lights didn't change colour, so I had to back-track, cast my net wider...