Keyboard cover left residue on keys

Hey y'all

I have had an unknown brand keyboard cover on my 2011 13 in. MBP for the past year or so. I decided that I no longer wanted to use it, so I took it off. The problem is, it seems to have left some kind of residue, almost like a soft adhesive, on the faces of multiple keys. It isn't so much sticky as it is abrasive in a way, similar to wiping a dry finger across tight cellophane. I suppose it isn't a big deal, but I would like some recommendations on how to best rid my keys of this residue.

Also, the main reason I removed the keyboard cover was because I had read that they can be damaging to the display because they may press on the screen when the "lid" is closed. Is this true, or should I not be worrying myself in the first place?

Thanks, all.