Paint won't hold up very well. Even factory applied black finish knobs get scratched easily. Agree with LWO...buy new hardware.

I would try Rub and Buff. It may or may not work. Rub and Buff works best when the surface is not completely smooth.

Black knobs are cheap. Get new ones. Paint will never hold.

I own a rental house, in which a former tenant thought it would be nice to paint the kitchen pulls scarlet (Go Bucks!). The guy worked on cars as a hobby, and he must have used auto paint. Those pulls are in great shape, years later. Try an epoxy appliance paint.

If you have a kitchen full of brushed chrome from 1970's era (or so)....why alter them? Sell them on eBay and get yourself the update you desire.

I used black spray paint on cup pulls. It lasted about 10 years.