Small parts that you need semi gloss black can be done using a Preval Sprayer and real automotive paint.
I use a mini Sata Jet. Works great for spot touch ups.
My auto paint store can make a pint of semi gloss acrylic enamel or Uerethane for a small price.
40-50 bucks spent but you get paint that lasts, doesn't fade, durable and better resistsance to the elements.
Yes it's a little more work and expense but it's worth it.
In the past, I painted my pulleys with rattle can paint.
A few years later, they looked dingy once again. Just not worth it.