I used to be one, Back In The Day, and it looks like my chops aren't entirely decayed. #1 Son was reading through his Cisco CCNA training book and got stuck on subnetting. Conceptually, he wasn't getting the mechanics. So I sat down with him and explained the background (the why/so what/who cares), and suddenly saw the light bulb go off over his head. Go team nerd!
Well the next day he said he didn't get route aggregation. Oops, I thought - didn't know this, and so sat down to read his book. Turns out I *did* now it, just that we used to call it "supernetting". And so I explained the background/why/so what/who cares, and suddenly saw the light bulb go off over his head again.
Go team me.
Interestingly, in both cases the trick was to get him to stop thinking in decimal and to write all the addresses down in binary (seriously). As I told him, you have to think like a router to understand why this works.
UPDATE 16 May 2014 14:28: There's a neat shortcut for calculating supernets here. Triple propeller head stuff, but nifty.