1915 Gas Tank

I have my gas tank for cleaning.
It has a small amount of rust and I thought that I would soak the inside over nite with vinegar.
Is this the way to clean it?
Anything else that I should do?
Should I paint the outside black or silver?

Vinegar might do the trick, worth a try. Originally the gas tanks were galvanized. Normally there is no reason to paint the outside.