Originally Posted by mstateglfr

For a whole frame-

1- buy Evaporust from an autoparts store.
2- pour 5ish ounces into a steel bowl and drop 20 paper towels in the liquid.
3- lightly squeeze excess liquid out of each and wrap the entire frame with paper towels. you can cut them in thinner pieces too.
4- cover frame with a couple garbage bags and wait 3-12 hours depending on the rust. the bags keep it from drying out and keeps everything clean.
5- rinse frame with clean water and dry.

Its pretty straight forward and doesn't take a ton of prep. just make sure the towels are wrapped tightly. This removes surface rust quickly and if you have any stubborn areas, you can spot treat it with a paper towel or two and cover with clingwrap.
You can reuse the liquid a few times too. Its great for rust on components and loosens all the crud in derailleurs etc without any effort on your part.
This process means no scrubbing with steel wool/tinfoil/anything that could scratch the paint. It also does not affect any paint or decals, at least so far.