Enugu handling
I have been in there many times with a foreign register. It was a fairly simple and straight forward exercise.
The people collecting landing, parking and pax tax comes to the aircraft and collects. Then pay your Nav charges in the building before filing a flight plan.
Being friendly and offering a cool drink to the people was enough in my experience.
Evergreen Apple will probably charge you excessively for what you could do yourself at a relatively small airfield.
Don't get a fright when you see the Conoil bowser!!! Fuel can be delay a bit so make sure you contact them in advance with your ETA.