Like any other paint job ,the finish reflects the prep.
Super clean engine first: so the oils dont keep getting pushed around on prep'd surfaces
Light sand every surface to remove stubborn oxidation and provide "tooth for new paint
Blow the hell out of it .leave no dust behind, some compressors can leave oily/ watery residue, depending on it's condition. I use a brake cleaner at this point ( Important be sure that you use the brake cleaner that does not take the paint off, or you'll be doing it over!) be sure you have tested your cleaner to see if it bubbles up paint before you spray the whole motor
Clean up : very important, physically clean and chemically clean, with "tooth" there is no reason for paint not to stick.
Use the green paint tape around parts that you don't want paint on, it sticks better than blue tape and doesn't bleed through.
High temp paint- 3 light coats then i solid finish coat I use a hairdryer at all stages here ... stops drips , drys paint and sets the paint with a little heat.
While you have the motor out ,this will be cake , have fun.