Lots of options already and it's likely I'm posting too late to do you any good but here goes my 2 cents.
For any gunk, I'd be using various solvents or detergents like already mentioned. i.e. Hoppes, Kroil, Simple Green etc. along with a scotch brite pad or some 0000 steel wool. Water won't hurt the metal if you use something to either dry it or displace the water after you are done.
For the rust, I've been using some really cool stuff for a while now that will remove all rust with zero effort, just a little time to soak. It's called "Evapo-Rust" and is pretty much totally harmless to get on you, you don't need gloves or a mask either. Just soak the parts until the rust is gone and then rinse with water. I've been using the heck out of it on used reloading dies I buy for cheap because they have light surface rust and they come out like new.
If you are interested, I did a "product review" on another forum. I don't have anything to do with the product but the forum was new at the time and they were asking members to review items they used related to shooting so I did the Evapo-Rust review. Anyway, here's a link.
http://www.marlinowners.com/forum/h...ories/74858-evapo-rust-review-dave-bulla.html
Oh, one thing I need to mention though. Since doing the review I've experimented a little bit more to determine if this stuff will remove blueing on gun parts or make parts change color. I've done quite a few of the old Lee Loader kits which have some parts blued and some not. I've decided that it WILL take off the blue (at least on the Lee parts, never tried it on an actual gun part) but I've also found that it will blacken some parts. Namely anything that is "hardened" steel.
An example would be the bits that go in a ratcheting screwdriver. I had a bunch of them that got all rusted in a toolbox and when I soaked them in Evapo-Rust, they came out perfectly rust free and jet black. I also did some snap ring pliers of the non interchangeable tip type. All of the black (I assume the industrial black finish on these tools is just a form of blueing) on the pliers came off but the actual tips that are hardened turned black.
Anyway, most auto part stores have it (for sure O'Reilly's) and it runs about $18 for a gallon but also comes in quart size for around $7 or $8. I run mine through a paper towel or coffee filter and put it back in the jug. I've used it maybe ten or fifteen times and it has darkened some and has an odor but it still works.
