I have some low cost black rotors and drum brakes.
1 clean with soap & water.. use a spray washer such as the local car wash or pressure washer if you have.
2 soak the rotors or drums in phosphoric acid. You can get this at your local hardware store or feed & grain....
Homedespot or Bows (also called The Orange warehouse or The Blue warehouse). Or just use Coca-Cola...
3 Rinse with clean water and air dry...for rapid drying, coat with 90% isopropyl alcohol ( rubbing alcohol ). See Note
Note:Do Not the drinking kind for this step...that would be alcohol abuse and we dont want that.
Next coat each part With...
Black brake rotor mix
Now for that slick shine. Coat each part with a little Water Displacement-40.
It will not last long or degrade your braking but makes it look professional until road grime does its work.
Or just a quick coat of deisel, or kerosene, or lamp oil.
Just wipe the brake shoe surface or pad surface with a little brake clean/ degreaser before installing