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I use microfiber. If that isn't sufficient then you probably need a cleaning solution to deal with the grease and dirt. There are tons of options. Just be careful and select one that isn't too strong.
 
A Mr. Clean Eraser has become my best friend. Although getting the crap from beneath the keys is another story. I have yet to figure that one out.
 
Um, I dunno if you should be using the Mr Clean. It's really abrasive, but works.
 
Um, I dunno if you should be using the Mr Clean. It's really abrasive, but works.

I know its super abrasive, but given the keys are black I figured if done lightly and because it isnt as wet as the cleaning cloths it really is the most effective way to get rid of not only my greasy finger gunk, but the shine left after you had already cleaned it.
 
I use Kleen and Dry isopropyl wipes for the body and keys. Just keep them off the screen (ironically what they were made for- they just don't go well with the screen's coating).
 
I usually use a paper towel and some rubbing alcohol. Just enough to get it damp. Then run it all over the keys. Nice and clean. Works even better on the white desktop keyboards to remove the dirt that accumulates over time.
 
A very soft toothbrush works well, with a bit of rubbing alcohol.
 
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