Ongoing - DIY DAZ Studio Basic IBL: Shader Mixer, to Shader Builder, to Pulling My Hair Out!

I was progressing nicely with my attempts to get a Shader Mixer based solution thanks to some helpful folks on DAZ3D's DAZ Studio forum - see my Shader Mixer (DS3+4): How to make a very basic diffuse IBL? thread.

Around post #17 to 18 I was beginning to think I needed to use Shader Builder instead, and by post #20 and 21 I thought I was almost there with a Shader Builder solution.

But I've run into some really, really basic problems with Shader Builder due to the lack of any detailed documentation. Same problem as Shader Mixer. The best official documentation I can find is this:

Shader Mixer documentation at the old Artzone wiki

Shader Builder documentation at the old Artzone wiki

Both these old Artzone software guides are marked as being 'in progress' and it's a 99.9%+ certainty that those particular documents won't ever be updated (because the old Artzone wiki was for DAZ Studio 3, and DAZ no longer support that).

Sadly, if you do a Google search for Shader Mixer documentation or Shader Builder Documentation those old Artzone wikis come at (or near) the top of the list). 

So I've started a new Shader Builder Queries - One Problem, One Post thread in the Nuts'n'Bolts forum at DAZ3D site, on the grounds that this is driving me nuts! ;o)

The DAZ 4.5 Shader Builder Tutorial - MK Gooch Shader by LJ Studios (aka DollyGirl) at ShareCG is definitely worth a look. Although I haven't found solution to my specific problems yet...

There's also a  Shader Mixer Tutorial I by ZigGraphix at DAZ3D and I think it's genuinely free - i.e. you don't have to be a PC member, and you don't have to buy something else first