Once dried, I cleaned up the block with a wire brush to knock any extra off then de-greased it again.
The second picture here is some Purple Power De-ruster at work. This stuff is a phosphoric acid mixture that will eat and convert rust while sealing it off so the rust can't continue to grow. I tested the coating it leaves with open flame from a torch which showed excellent resistance to heat.
I then moved to taping it off and priming it with Dupli-Color Engine Primer.
The engine enamels have a strange curing window that must be observed other wise the paint doesn't cure right and looks like garbage so follow the instructions closely.
On a side note, looking back, I wish I had scuffed the de-ruster layer much better. I think if I were to do it again I would still use the de-ruster but would have scuffed it with a brass wire brush. The coating is quite durable.