Got the cases back now. They did an aggressive blasting to try and eliminate all the corrosion. Mostly this has worked well but still a few places where I'm going to have to wet and dry.
In any case (get it?) it's a good finish for painting. The cam cover I have painted as my test piece using VHT paints; Engine Enamel Primer, Barrel Paint and Satin Clear Clear. Comes up good.
And a reminder of what I started with: