​My previous SketchFab model uploads were really only a way for me to dip my toe into the water.  This time I went for the whole foot, maybe even half-calf!  I attempted to upload my farm house model to SketchFab.  This model had two particle systems and multiple texture- and procedurally-based materials.  I'm considering the attempt a success, primarily because I was able to get to a semi-workable model, but there were plenty of Opportunities To Excel along the way! :)

Lessons Learned 

1. ​  SketchFab can import Blender files (Hooray!).....except when the latest (eagerly awaited) update totally changes the file format.   This took me a while to understand because SketchFab says they import Blender files, and I was sure I had uploaded Blender files previously.  This was my first attempt to upload a Blender 2.8 file format, and 2.8 is still in Beta testing.  I'm sure the importer will be updated when 2.8 is officially released.  In the meantime, I uploaded an .OBJ file which worked fine.
2. The beauty of Blender particle systems is they keep file size small because they don't really create all those objects until you need them; the gross injustice of Blender particle systems is they trick you into thinking something is really there when it isn't!  I had some tree leaves and tall grass that really added something to the model (IMHO), but I neglected to apply those particle systems before uploading.  Definitely next time....
3. Physically Based Rendering (PBR) materials are everywhere!  Blender has them, SketchFab has them.  It should be a one-to-one transfer to get the materials out of one and into the other.   Not so much.  However, it was simple to import the material textures into SketchFab.  The scaling, UV mapping, etc. all transferred, so it was simple matter of importing the image file.  The procedurally based PBR materials were not quite as straightforward.  I think I will remind future me to create an image texture of the PBR nodes in Blender so I can easily import that image file with the model.

All-in-all, I won't call this my greatest work, but it is a significant increase in complexity over previous models I've uploaded, and it looks good enough.  And a win is a win!