First make sure you have a set worth restoring. Rust pitting is difficult to impossible to hide on these items and make sure the short leaf is the correct one for your car and they haven't been replaced.
After disassemblying and cleaning (removing grease, oil and or rust) many are dying/treating them with a bath of Insta-black or doing the home phosphating so they can keep the temp down as to not affect the springs. Since they are so long it can be difficult to get an even look and finish across the whole surface using some of the other treatments and products
Then reassemblying them with new correct clamps, replacing the paint marks then oiling them