Unless your using a high pressure cleaner for the engine bay hosing down the engine shouldnt prove to hazardous. Just make sure water isnt lingering in your dizzy cap, and around other electrical components, i.e. coil, battery terminals.
If you use a degreaser make sure you dont use it on a hot motor and rinse it off well or otherwise your engine will stink of degreaser for a week or 2 whenever you drive it.
if you remove the rocker cover for painting you can just close the bonnet to prevent shit landing in your head, if its gonna be off for a while you can always cover it with a sheet or plastic etc.
When painting your cover make sure the surfaces that make contact with gaskets remain unpainted (what i did was leave the old rocker cover gasket in the cover itself and sprayed it, then removed the old gasket along with any overspray that might have made its way to where the gasket sits then replaced it with a new one.)
apart from that your bay looks pretty clean anyway...