I gave this thing the full works. They were originally dirty with diesel soot.
I started by fully dissembling the horn. Cleaned and inspected each diaphragm.
Then i used a wire brush wheel on each bell to clean off the soot and dirt.
After i used 60 grit sand paper, then 220 grit, then 440 grit on each bell.
The finish is bare aluminum and they are ready for a fresh coat of paint or powder coat.