I have used brake cleaner and a solvent brush to clean off the crud.Make sure the engine block is warmed up some before you paint it so the paint sticks better.
I use pieces of newspaper and cardboard to block the overspray where needed.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!