Help with updating hardware

Hello all, me again looking for some advice. We're trying to do some small updates around our home and aren't sure how to approach them.

I'm interested in painting the brass trim around a mirrored bifold door. Do I need to lightly sand or use a fine steel wool on the brass first? Do I need a primer? What paint to do you recommend for the trim?

Second, I'd like to repaint my bathroom hardware. What sort of prep do I need to do to those pieces? (Sand or steel wool. Do I need a primer?) What recommendation for paint & color do you have for bathroom hardware? (attached some photos so you can see what I'm working with!)

TIA!