Do it yourself...it's fun and very easy to do.
Remove the knobs.
1. On a newspaper-covered surface, brush the knobs with lacquer remover. (
acetone)
2. After the coating is loosened, use
grade 0000 steel wool to remove the coating and to polish the brass surface.
3. Rinse the lacquer remover from the brass with a mild soap solution.
4. Apply a high quality, non abrasive,
polymer-base automobile wax to seal the surface.
5. Alternatively, you can apply a
spray lacquer, but this is more likely to flake off down the road. Though waxing requires continuous care, spray lacquer tends to be a bigger mess to clean up later.