hey folks, quick question. I have a black indoor metal rail going up my steps. it is a flat black, want to either touch up or repaint it. should I use a gloss,semi gloss or flat paint for this project ?. i did touch up the scratches with gloss black rsutoleum,but looks goofy ,please help

I would sand it lightly and then wipe down with paint thinner and follow this with an ammonia and water wash to remove hand oils. The finish paint should be an oil based enamel and i would think that a semi-gloss or gloss would hold up better than a flat finish.