You may wish to consult with a local auto body supply store regarding your rehab ideas.
If the pitting is rather small, auto body glaziers putty or spot putty, available in a small tube, might meet your needs. If the paint is still solidly attached, a light wet sanding of the components with 400/600 wet-or-dry should provide a good base for primer-putty-primer-paint.
BMW handlebar elements appear, to me, to be something like a semi-flat black. Neither glossy nor flat. On my R65, I have found the rattle can Semi-Flat Black Ace Hardware brand spray paint to be a very good match for chassis components.
The final paint is the easy part. Prep work, and lots of it, will ensure you only paint once. BTW, there's perhaps the option of powder coating... if it'll adhere to filled and primered parts. I dunno 'bout dat..