The title says it all! How do you do it to a DM?
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Well if you want to do it for free with things you usually have in your house here’s a pretty good vid. I use this method and it works for me.
Hope this helps and good luck! 
Here is a guide for it on YYN:
http://www.yoyonation.com/talk/index.php/topic,1189.0.html
Kim-Lan! Now that you posted, I realized you were gone…
I was?
If you are unsure about the baking soda you can always use a MR CLEAN MAGIC ERASER, they work jsut as good, and they are much easier to use
Well, I didn’t see you posting…
Here’s a decent video:
Hey, what i do is the same but i suggest you dont use sand paper that is real ruff it could scratch up the yoyo so first make sure its metal take the most less sand paper you could find and rub agianst rims slowly and with a little pressure and so on so forth after a while you will notice your rims are shiny ;D and go over every section 
in the yoyonation post, i have results from my hitman, and i used sand paper fromm 120 grit, all the way up to 2000 grit, then i used steel wool, then you polish it with chemicals… then a perfect shine, i actually need to do i again, but im so busy, with the whole string making thing.