Alrighty, here is the result. Most of the rust was removed from the engine shroud, bar a couple of small spots with paint. Most of the old paint peeled off easily but I used the pressure washer to remove most of the rest. Then used steel wool. As it air dried, the iron oxide rapidly reappeared, so I used CLR and a blue scouring pad to wipe it off before rinsing and quickly drying it with a clean rag, before using a hairdryer for a few minutes. Then out with the can of black zinc paint. The paint revealed some pitting in the finish from years of rust, but that will be mostly hidden by the plastic dress cowl. Metal is hard work to clean up and repaint. Wow.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!