I recently learned a trick from a Starrett customer support person, when my combination square started to rust. She suggested using green Scotch Brite pads with 3-in-1 oil to clean them up. I bought a six pack of Scotch Brite Heavy Duty Scour Pads at Home Depot for $5. Combined with the oil, they worked like a charm. I have used them to clean off the rust and cruft from many hand tools, including hand planes. They work great.
Keep in mind that different Scotch Brite pads can be more or less abrasive. The ones I got at Home Depot are quite abrasive and leave a scratchy, powdery residue. An air hose and a stiff nylon brush might be helpful to clean up the abrasive powder. I read somewhere that some Scotch Brite pads are impregnated with corundum / aluminum oxide. (I am sorry, but I can't locate the source.) It is the same stuff they use on some types of sandpaper. Those Scotch Brite pads can put scratches on polished metal surfaces.
In addition, I just learned about Renaissance Wax, which protects hand tools after you clean them up. It works well for me.
I hope this helps.