Polishing parts is a very good idea to save pieces that you might otherwise think are junk. This is especially helpful with internal engine components and hardware. I have been doing a few different techniques lately to restore the beauty in parts and I have found that nothing works better than a bench grinder that has dual wheels. One wheel is typically a graphite stone grinder (DON'T USE THIS SIDE! YOU WILL ACTUALLY TAKE METAL OFF AND THIN YOUR PARTS!) and the other wheel is a heavy duty wire polisher (the side we will be dealing with). This tool is an extremely expensive investment, so if you don't already have one, you might want to try and make friends with some one that does! Luckily, my step-father has one. I can't even begin to explain how well this method works. Last weekend I used it on my gear selector, my clutch cover, my piston, and my cylinder and some random hardware. These parts were rusty, grimy, and extremely dirty. Now they look like they just rolled off of the factory assembly line.
Today, I tried to use a dremel with wire grinding tips to polish some parts. I don't recommend this method at all except for maybe very mild use to get into crevasses that you can't reach with the bench grinder. It works pretty well, but little bits of wire fly off of the dremel bits until all of the wires are gone and you're left with nothing. And this isn't a slow process. I bought two bits this afternoon. Within an hour of usage, both bits were reduced to nothing. So, don't do this more than necessary. Because of little wire fragments flying everywhere, I would especially not use this method on internal engine components as an alternative to taking the parts out of the case and using a bench grinder. It is absolutely crucial that the inside of the engine is COMPLETELY free of debris when reassembling it. And this frankly can't be accomplished with all of those little bits of wire flying inside the case. Take the time to take out the individual pieces and use the bench grinder. Your engine will thank you.
You may be tempted to wire polish your casings. While this will look very nice, a lot of people don't recommend it. Jeremy's blog goes into detail about it, but simply put; the engine case will get dirty, and fast. If you don't want to clean your engine case every day of your life, don't set it up for these high standards. Media blasting or a good scrubbing with paint thinner is sufficient.