Let's see here.... Prepping: the bottom line on this is that the part should be smooth and COMPLETELY oil & dirt free. Bare metal is best, but not usually necessary. Chemical strippers with methylene chloride (aka dichloromethane) + light sanding works. You can also just use sandpaper starting with maybe 180-grit and going down to at least 1000-grit. If you leave paint, it should be very well adhered and sanded smooth & clean of oil/dirt.

Primers help some paints stick better to bare metal. "Filling" primers can also cover some small scratches from sanding. Using primer is better than not using it, but in this application you don't "need" it unless you go down to bare metal with sandblasting or a chemical stripper. Make sure that if you use primer, you get the same brand of primer as the brand of color paint you use. "Occasionally" there are some incompatibility problems with primers/color coats from different manufacturers (rare, but it happens).

For the color coats, apply it IN VERY THIN 1/2-COATS & LET IT 1/2-DRY ("flash") BETWEEN COATS. The natural tendency is to try to cover everything in 1-coat and that is what causes runs, solvent pop & all sorts of problems. Use very light coats. You keep on putting on light coats until everything looks even. You'll likely have to use more coats on the orange lid than the black base since black pigments "hide" much better than orange pigments (part of paint that makes the color).