Such a beautiful engine, and your setup is impressive. I haven't steamed mine yet, I've only run it on air. Maybe there is an easier way to get the water pump pumping, maybe priming it before startup? Nice video.
It's always been a little problematic getting it primed, when I used the syringe in the vid (first time I've done that) it started up pretty much straight away. So pre-priming might be the go.