Came across a fun freebie on SCG, a bust and plinth.
https://sharecg.com/v/71813/related...st_MC-Character

Ooh, that would look so good with 'zombie' eyes ! How hard could it be ??

Although labelled as a DS model, bust and plinth were also supplied as OBJs, without MTL. I soon discovered the supplied 'Diffuse' and 'Bump' maps were a scatter of fragments that bore scant resemblance to the figure until applied.

After wrangling free UV Mapper Classic, I accidentally generated a square texture map I could navigate. I belatedly discovered that mapping a model is not sufficient, you also have to save that mapped model so map and mapped mesh align. Sadly, the map was was squashed sideways, making eye-balls and pupils egg-shaped. After several tries, I found that re-sizing map at 2w:1h made the eyes and pupils 'round enough'. I tried painting by eye with free Irfan View ('IV'), was 'off' just enough to look silly. IV does not support 'layers' per eg photoshop, so I could not use the map as a guide to build concentric zones.

After some head-scratching, I wondered if I could use IV's 'water-mark' tool, which overlays one pic with another. Scaling and degree of 'marking' adjustable...

The existing textures were mapped, so did not tile. I soon found a nice 'Rock High Res.jpg' with similar hue to let me continue. After several attempts, I managed to overlay this texture with  barely visible map.

But, again, my hand-painted map was just 'off' enough to look silly. Specifically, pupils did not align with their estimated texture.

Time for Plan_B: If I could separate the eyes' irises and pupils from the rest of bust, I should be able to paint them more convincingly. A huge fight ensued with my ($$) TurboCad_2016.

First, I had to 'explode' the OBJ from a single surface to a polygon mesh. Then, I began carving at bust, shifting my off-cuts to a 'hidden layer' until only the eyeballs were left. Unfortunately, each such scrap would become a sub-object, and we were talking dozen. Worse, the 3D Slice tool ran into same problem as a decade ago, TC suddenly deciding the remaining mesh was not suitable for Slicing or any other 3D Boolean....

I re-started several times, each one making fewer and fewer cuts, but I could not isolate the eye-balls before the Booleans 'locked up'.

Then, a light-bulb moment: Perhaps the eye-balls were already 'grouped' ? Restart, explode, export as modified OBJ, check...

Aha ! This time, the eyeballs appeared as individual 'groups'. Into UV Mapper Classic, where map 'tiled by group' now has the bust with two stand-alone round eyeballs...

Save map, save mapped mesh. Several tries later, I've applied rock texture, yellow iris, black pupil to this map and the figure looks nicely ominous...
( Click to enlarge...)

 

Very spooky looking.

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I've found that to do well with any figure you really need to have a passion for that figure,

...and I hope you develop that passion for yours.

Thank you kindly Nik, I appreciate your explanations, giving me insight