I will pass on the philosophies, so what I do is this. I use the bio degradable cleaners, like the various green stuff, power wash, and spot clean with carb cleaner or the green stuff in a spray bottle. When I have cleaned until I am satisfied, I wipe the engine down with mineral spirits. The spirits work very well. Next I brush on a good paint that will take some heat.
Unless you dunk the engine in a tank during the rebuilding process or have access to a steam cleaner, this is about the only way I know to clean it up. It is tedious and not the most amount of fun you can have, but it works.
