A few years ago we started restoring an AWT AccuPrint AP-2538. The entire machine was rusted over when we first found it, still functional, but very dirty.
After almost destroying it during transport (oops) we unloaded it into our print shop and started taking it apart. Using white vinegar, I de-rusted every piece of metal I could fit into a bucket. I sat in my garage and listened to music, and just scrubbed away. It probably took me about three weeks to finish scrubbing and rehydrating the metal and plastic in mineral oil.
We put it back together and it looked absolutely beautiful!