Ok. I bought some “dark tone” ink, which I felt was not dark enough once I diluted it a bit. So I added some black inkjet printer ink. Then I redid just the base of the pieces.
Better, I think. But the ink doesn’t cling to the cracks as I would like it to. Perhaps it needs some paint, rather than being just ink and water. Paint, and I need to brush it off the surface and let it set for a moment before drying it.
In any case, I am finished dicking around with step 4. Step 5 – the drybrush – is next, and it will lighten the floors and walls and make them look heaps better.