Semi-gloss and satin are the same thing. I personally think Rustoleum paint holds up fine. Most agree it should be the semi-gloss or satin black paint on all the parts you mentioned.
I have found that buying the Rustoleum in the qaurt cans and using my HVLP spray gun is the most cost affective way to apply the paint to larger pieces/surfaces (it sprays nicely when thinned per instructions, but it takes a long time to dry). I use disposable cups on the gun to minimize solvent waste for cleaning.
