First thing is, make sure the blade is worth all of the effort you are about to put into it. Another thing to know is, the harder the metal, the better the polish will come out but also the longer it may take to do so. So, look at your blade. Is it realy scratched up? With deep scratches and gouges? To ,irror polish something like this you will have to remove material to the depth of the scratch and a little more. Not always the best thing to do nor worth doing. If you have a valuable blade worth decent money I would say..do not do anything to it at all besides a little mineral oil on the blade. Anyhow, despit all of that here is what I did. I have an old wolf cutlery knife about 1 ft long in actualy blade lenght and very thick and sturdy and made with a high carbon steel. The blade had some scratches, lol more than one but not any of them too deep and only a little pitting. I started with a 400 grit wet dry paper and kjeeping in one direction with a little water sanded for an hour here and an hour there until the knife blade had a uniform rroughness according to the grit I was using.
I then changed to 600 grit and did the same thing, taking that sanding polish smoothly and cleanly to that grit. I then went to 1,200 grit and finshed with 2,000 grit. After all of this I switched to a drummel with a polishing buffer head and used white stick which is used to plish platuinum or very hard metals. I am sorry I can not seem to get a proper photo to do it justice. Why did I go through all of this effort? The blade is going to be engraved. When that is done, after the artist had used an acid to darken the whole blade and buffed it out leaving the contrast that I want. Then all the effort that i went through shows. You will have the mnirror plolish of the unengraved areas with the dark contast of the engraved areas creating a near three dee look. When engraving is done I will post another picture.