How to clean the Dell i7559-2512BLK?

First of all, the casing has some kind of rubber coating all over it. It feels really nice and it looks super cool, so I'm worried rubbing alcohol or something might ruin the texture/aesthetic of it. What can I safely wipe the laptop down with to remove fingerprints without fear of deteriorating the material?

Also, I seem to have a couple of crumbs in the top-facing speaker. I don't know how they got there, and I don't know how to get them out. 

Thanks!