oldiron, others will chime in with suggestions for paint/painting. But over the decades I got tired of paint looking lousy and not lasting. So a couple of decades ago I cleaned and thoroughly polished my caps, and then carefully cut and applied black trim tape. It sticks much better than paint and obviously lasts longer. The process is exceedingly meticulous, but the results are worth it. I started by making paper templates, cut the pieces and carefully fit them. A nice winter project.