Oh well, we live and learn. Looking at the Sarmatians I ink-washed yesterday, the wash seems to have stained the gesso primer rather than settling nicely into the recesses. I tried another wash-mix (higher matte medium percentage) and that went on like paint! I guess that gesso must have more "tooth" than the primers I've used before. The detail is pretty clear anyway, so the initial wash is probably unnecessary.
Note to self: skip the post-priming wash step!
And now for some pictorial silliness for you. Despite all the advances in military technology, theory and practice, it seems that some NCOs are still stuck in the 19th Century: