Do a search for oxalic acid. Many people have used it with great success for removing rust from rusty bicycle parts. They even treat frames and forks. You'll probably find pictures, too. You can buy it as a powder on eBay. You can also buy it in the form of deck cleaner. You soak the parts in a weak solution until the rust is gone. Protecting the resulting bare metal is a problem, but I can't see painting each pit in the part with grey primer and a Q-tip as a practical solution.