Gross but practical question: how do you keep your external keyboard / mouse clean? 

I've tried isopropyl wipes and it doesn't seem that effective.

I have the same keyboard at work and at home but the one at home feels 100x nicer since I use it so much less.

Is it a lost cause?

Since it's mostly lipids, use warm dish soap. Alcohol isn't very good as a solvent for grease.

This is the way, honestly. If you can remove the keycaps and wash them in a bowl with soap, even better. But I think he uses the Apple keyboard