You could clear lacquer the bell to protect your hard work.
To be honest I’d intended to paint it all , but when I gave it a bit of a rub with wire wool hey presto it came up like this. It didn’t take more than an hour to clean up the aluminium part. The car is not a daily driver and is garaged so doesn’t have a hard life. As I take the wheels off pretty regularly I’ll see how they weather and hopefully a regular rub over with wire wool will keep them looking good.