Im really not going to be the best person to address your question. One of the things Ive learned in collecting somethings. More items have had their value permanently diminished by improper cleaning than maintained or improved. If you were to look at my own collection of knives, youd notice that most of them seem to have acquired what Ill call a lot of character. Another way of saying it is they have that been there done that look. What I do go after is dirt, and active rust ( this includes the green corrosion called verdigris that you see on copper and brass items). Im not trying to make the item look brand new. Im trying to preserve it. What your talking about is more in the subject of restoration than preservation. Restoration is very controversial and very complex. I really feel Im very low on the learning curve in regards to restoration. My own priority has been to avoid damaging the original item. This tends to lead me in the direction of leaving alone the things that have accumulated with the item over time. After all its part of that items story. The above being said Ill share the following. Please keep in mind that this is nothing more than an opinion. You can find different ones and they could be much better. With a high carbon steel blade that shows discoloration and possible corrosion: I use a product named Kroil. Its a very good penetrating oil. If you cant find it in your area you should be able to find an acceptable substitute at an auto supply store. Your not likely to get Kroil at the auto supply store. Id do a search for it on the net look for local suppliers or order it direct. I prefer the liquid version and not the aerosol. I believe you get more product for your money. Wipe some of the oil on the steel and let it sit for awhile. A little bit goes a long way and after about ten minutes or so should be as long as you have to wait. If you can let it stand longer thats not bad either. After about 30 minutes I wouldnt think your gaining much waiting longer. Scrub the steel with a coarse cotton cloth or rag. Be careful here the thing does have an edge on it. Youll notice the rag is picking up dirt. Also if your getting dirt on the rag that is brown in color your getting rust off the steel. It may not have been readily apparent just looking at the blade. This isnt going to remove the discoloration from the blade in most cases as its really loosening the stuff that has gotten on the surface and make it easier to remove. If you feel that the rag isnt enough I would recommend not using an item any coarser than #0000 steel wool on the surface of the steel. you can add a little oil to the steel wool and scrub away. Wiping the surface of the steel with a rag or even paper towel will lift the dirt. A side benefit to the oil is that it will provide shielding to the steel from the atmosphere. It may not be the best choose for this but its better than nothing. Also when you wipe it off it will leave a little behind. Regarding cleaning the brass. I dont like to remove the brown that develops on brass. To me its the natural patina of the brass and I like to keep it as is. Verdigris, the green that can form on brass is a different thing to me. In either case once you remove what you want to get rid of the problem is what to do to keep it from returning. The answer is imperfect and requires that what ever you do you will have to keep an eye on the brass and except that someday your going to have to do it again. The key is to seal the surface of the brass from the atmosphere. My own best results have been to coat the brass with a clear wax. In general I do this with the whole knife. Stay away from waxes from the auto supply store. Most of these have fine abrasives added to them to help in the polishing of the auto finish. IMHO not what you want. One of the most recommended is Renaissance Wax. In regards to preservation Im not sure you can find anything better. The stuff is expensive and hard to find. Ive had results that Im happy with, (to this point), with clear waxes that have a good amount of carnauba in them. I often use Johnsons Paste Wax. At the end of the day its your knife and you are the only one who can say what it is you want. Sorry for the long post. I hope there might be something in it that will be of value.