Tim -
I cleaned on my 235 for a few days to try to remove all grease and oil. Let it dry it thoughly, then painted it before oil started seeping out of any leaky gaskets.
I removed the valve cover and push rod cover. Primed them with self-etching primer, sprayed sandable primer, and then wet sanded. Looks good, especially if there are rust pits on them. I used Duplicolor engine primer on the covers and on the entire engine before shooting with Filling Station gray. Primers and engine paint were all in rattle-cans. I also bought a pint of brushable engine paint for the hard to reach areas. An HVLP gun on an engine that is on an engine stand would be much better than rattle cans.
Are you painting the engines while they are in the trucks or out? I painted mine without removing from the truck. I didn't have a good plan - if that is even possible. I spent 90% of my time masking, 10% painting, then back to 90/10 mask/paint to repaint overspray items. Then again and again and again.
> Masked> Finished